Genetics Exam 1

Genetics is the science of

heredity

What are three subsections of genetics?

-transmission, molecular and population

Transmission genetics deals with

offspring/parent

Population genetics deals with

groups of species

molecular genetics deals with

DNA structure

Define pangenesis

genetic information travels from different parts of the body to reproductive organs

Define performationism

miniature organism resdes in sex cells, and all traits are inherited from one parent

Define inheritance of acquired traits

acquired traits become incorporated into hereditary information

Define blending inheritance

all genes blend and combined, can never be seperated/irrersible

Which early concepts of heredity were correct?

Germ-plasm theory, cell theory and mendelian inheritance

Define the germ-plasm theory

all cells contain a complete set of genetic information

Define cell theory

all life is composed of cells, and cells arise only from cells

Define mendelian inhertiance

traits are inhertied in accord with define principles

Genetics and the study of heredity is really about the patterns of inheritance of what macromolecule?

DNA

Which of the following is NOT found in a bacterial cell?

Nucleus

A chromosome that has a centromere positioned closed to, but not EXACTLY in the middle of the chromosome is called

submetacentric

Which of the following theories about heredity is correct?
A. Performationism
B. Blending Inheritance
C. Germ-plasm theory
D. Inhertiance of acquired characteristics
E. Pangenesis

Germ-plasm theory

What are some characteristics of prokaryotes?

-prototype
-before
-bacteria, archea
-membrane bags -DNA is free floating

In what pahse of the cell cycle is the DNA replicated?

S phase

A strawberry cell that is 8N divides by Mitosis. How many chromosomes will there be in each of the two daughter cells?

8N in each daughter cell

Homologous chromosomes first pair up in what stage of Meiosis?

Prophase I

4 genetically different cells are formed in what stage of Meiosis?

After Telophase

The first monoploid cells are first formed in what stage of Meiosis?

After Telophase

Chromosome tetrads line up in the center of the cell in what stage of Meiosi?

Metaphse I

What are some characteristics of eukaryotes?

- true + nucleus
- animal/plant cells
- contains DNA in nucleus
-membrane bound organelles

How is DNA structure in prokaryotes?

Not complex with histones in eubacteria, some histones in archea.

How is DNA structure in eukaryotes?

Complex in histones

What do prokaryotes lack that eukaryotes have?

membrane bound organelles and nucleus

Which aspects of porkaryotes are larger in eukaryotes?

cell diameter and amount of DNA

Which type of cell usually has one cicular DNA molecule?

prokaryote

Which type of cell has multiple linear DNA molecules?

eukaryote

What are some key differences between Prokaryotes and Eukaryotes?

- nucleus
- cell diameter
- genome
- DNA structure
- amount of DNA
-membrane bound organelles

DNA is found where in eukaryotes?

in the nucleus (nuclear chromosomes), in the mitochondira and chloroplasts (organelle DNA)

Where is DNA found in prokaryotes?

in the nucleoid

Define daughter cells

clones, genetically identical to each other and the starting cell

Why do cells divide?

- growth
- asexual reproduction
- replacing old cells (healing wounds)

Bacteria and some single celled eukaryotes divide with what type of cell division?

Binary fission

Mitosis and Meiosis use what type of chromosomes?

linear chromosomes

What is the result of binary fission?

two clone cells that each have a circle of DNA

What part of the DNA stretches and divides into two cells in binary fission?

origin of replication

Binary fission deals with which type of chromosomes?

circular chromosomes/DNA

Eukaryotes divide by what type of cell division?

mitosis

Mitosis grabs every chromosome to ensure what?

One copy of each chromosome goes into each cell

Define kinetochore

protein that go all the way around the centromere to form a ring, recognizes the sequence of centromeres (where microtubules attach).

telomere

Ends or zones with special DNA. Serves as a "cap", located on either end of linear chromosomes.

centromeres are located where in the chromosomes?

Somewhere in between, not always in the middle

What occurs during replication of DNA?

1 DNA goes to 2 DNA, the double helix is opene dup and new DNA build onto it (half old, half new)

What are some structures in a eukaryotic chromosome?

- telomere
- centromere
- kinetochore
- spinde microtubules

What are the four positions of centromeres?

- metacentric
- submetacentric
- arocentric
- telocentric

define cytogenetics

cell genetics, microscope level study of chromosomes

Define a metacentric centromere

exactly at the middle

Define a submetacentric centromere

not at the middle but close

Define a arocentric centromere

just below the telomere

Define a telocentric centromere

at the end, not all the way

How are karyotypes placed?

From longest to smallest, can also be arranged by the centromere location

The p arm in a chromosome

the short arm of a chromosome

What is the q arm in a chromosome?

long arm

How are chromosomes placed in terms of the q arm and the p arm?

the short arm (p) is placed up

What gives the chromosomes the banding pattern?

when they are stained

What do the bands mean in stained chromosomes?

How tight the chromosomes are packed

Define locus

place on DNA where the gene is found

How do you count chromosomes?

count the centromeres

In mitosis, seperates the duplicated chromosomes and each daughter cell gets what?

one centromere

Define ploidy (n)

the number if unique chromsomes for a particular species

Define monoploid/haploid

1x ploidy number (1n), monoploid number of chromosomes

Gametes in animals are

egg and sperm

Which type of cells in animals are only monoploid?

gametes/germ cells

Define diploid

2x ploidy number (2n). 2 copies of each unique chromosome

In animals which type of cells are diploid?

all somatic cells

What is the ploidy for humans (1n)

23

What happens if an embryo has too much genetic material or too little?

it will die

XX mean

female

XY means

male

The sex chromosomes are located where in a karyotype?

bottom row of karyotype

somatic cells are all cells in your body except for

eggs and sperm, germ cells

somatic cells contain what type of chromsomes?

homologous chromosomes with small variation

each set of chromosomes is a

homologous pair

In the m phase the cell

divides

What happens in the G1 phase?

growth phase, cell is doing the job is destined to do

How does a cell decide to divide or not?

It assess its environemnt, nutritins and space

In what phase does the cell decide to divide or not?

between G1 and S phase and G2 and M

What occurs in the S phase?

DNA synthesis/replication,

What phases are part of interphase?

G1, S, G2

What occurs in G2?

cell grows, all chromosomes are replicated, are divided into daughter cells

in mitosis, one cell forms

two identical daughter cells

What is mitosis important for?

-growth
-asexual reproduction (make another free living organism)
-replacement of old cells (heal wounds)

what occurs in interphase?

-chromosomes replicate and start to condense
-nuclear envelope is present
-centrosome duplicate (barrel shaped)

where are centromeres located?

on the chromosome, piched region

what are centrosomes?

whole sphere that surrounds individual centrioles

what are centrioles?

microtubule organizing centers, microtubles grow out of them

In animal cells what grows from centrosomes?

mitotic spindle

what do microtubules do?

protein fibers that help manipulate the chromosomes

what occurs in early prophase?

- centrosomes move to opposite poles and spindle starts to form
-chromosomes are visible as two sister chromatids attached at the centromere

what occurs in prometaphase?

-nuclear envelope has disintegrated
-chromosomes attach to the mitotic spindle
-cells move chromosomes around

what occurs in metaphase?

-chromosomes line up in the middle/equator or center of the cell
-chromosomes are pulled evenly by the microtubule spidles, end up in the cener of the cell in a total stalemate

what occurs in anaphase?

-spindle fibers pull back towards the centrosomes, pull chromosomes apart
-sister chromatids are separated from each other
-"away

what occurs in telophasae?

-"end"
-nuclear envelope reforms around the chromosomes
-microtubules collapse/dissamble
-no longer sister chromatids
-chromosomes stop moving
-some cells do cytokinesis at the same time

define karyokinesis

division of the genetic material (chromosomes)

define cytokinesis

division of the cytoplasm including any organelles

what occurs cytokinesis?

-cell membrane and cytoplasm + anything in the cytoplasm pinches in to form two cells. The cells are genetically identical

mitosis maintains what?

ploidy, 4 chromosomes in each daughter cells, same chromosomes from parent cells

in mitosis doesn't count chromosomes because they are

independent from each other

what happens in G0?

cells step out of the cell cycle from G1, may reenter G1

what stage of mitosis takes the longest?

prophase

length of the stages of mitosis vary between

species and cell types

What type of cells do mitosis?

somatic/body cells

Dolly the sheep was made with

an adult nucleus inside of an egg, tricked into being an embryoni nucleus

monkey clones were made with

a fetal nucleus into an adult cell

why are actual organs not succesfully cloned?

too complex to recreate

homologous chromosomes in a diploid organism have the same

array of genes, size and shape, banding.

homologous chromosomes are

one chromosome is maternal, the other is paternal

when an egg and a sperm go through fertilization they produce what?

zygote with 4 chromosomes

a zygote is

diploid, with homologous pairs, 2n

taking chromosomes from each parent creates

variation, mixes genes

why is variation needed when producing offspring?

helps create offpsring that is better than the parents and increases survivavility

meiosis consists of how many cell division?

two cell division

what is meiosis used for?

- sexual reproduction (gamete formation)
- introduction of variation of the genetic material, to not create clones
- maintaing the ploidy of the species following fertilization

In meiosis, a diploid 2n cell divides into

four 1n cells

what happens to the cell number/ploidy in meiosis?

it is dropped down, does not maintain ploidy

The first division, meiosis I is called a reduction division because

homologous chromosomes seperate, ploidy goes from 2n to 1n + 1n

the second division, meiosis ii is called an equational division because

equalizes the number of chromosomes
- one of every chromosome in a single form
-creates four 1n cells

What are the substages of prophase I?

Leptotene, zygotene, pachytene, diplotene, diakinesis

what occurs in meiosis i, prophase i?

-centrosomes move to opposite poles
-chromosomes begin to condense
-homologous chromosomes pair up and form a tetrad
-crossing over occurs between the sister chromatids

Where and when does crossing occur?

Late prophase, in the chiasma/chiasmata of the chroosomes

what is a tetrad?

4 chromosomes/sister chroomatids

when do homologous chromosomes first pair up?

prophase I

when does crossing over occur?

it occurs in prophase i

recombination of DNA occurs in prophase i through what process?

crossing over

How do homologous pairs form a tetrad?

through the synaptonemal complex

What is the synaptonemal complex?

protein/scaffolding that lines down the length of of the chromosomes and holds them together

What does the synaptonemal complex interact with?

the sister chromatids that are in the center/middle, each from a different chromosome

crossing over is facilitated by what?

the synaptonemal complex, which includes recombinase proteins

How exactly does the synaptonemal complex work?

holds the homologous pairs or tetrad together and lines them up gene for gene. Contains enzymes that facilitate the swapping of some of the portion of the SC between each other

what happens in metaphse i?

-chromosomes move to the middle as tetrads
-pushing/shoving of the chromosomes like in mitosis
-pairs of homologous chromosomes line up at the metaphase plate through connections to the spindle

what happens in anaphase i?

-microtubules seperate the tetrads
-homologous pairs seperate instead of seperating just one chromosome
- each chromosome goes to opposite poles of the cell

what happens in telophase i?

-chromosomes reach the end of the cell / spindle poles
-nuclear envelope reforms
-beginnings of cytokinesis can occur

what is interkinesis?

the time between mieosis i and meiosis ii

what doesn't occur in interkinesis?

chromosome replication before meiosis ii

cytokinesis occurs in most species to produce

two daughter cells

Some species proceed directly to Meiosis II without finishing what?

cytokinesis and forming full membranes between the cells

What is an example of a big delay between meiosis i and meiosis ii?

Human females

in human females, reduction division is done as

a fetus

When do human females complete meiosis ii?

when they hit puberty, once a month one 1n cells from MI finishes MII with ovulation

what is the finishing product of meiosis?

4 monoploid (1n) cells not identical to each other

in meiosis ii, the sister chromatid are

seperated into two

ploidy on meiosis is

fixed

How many cells does mitosis start off with and how many does it end with?

two cells, four cells

what is the product after telophase ii?

four nuclei, all 1n / monoploid

meiosis ii final products are

four monoploid ceoos, with a new combination of maternal and paternal genetic information i.e. genetically unique

a chromosome of 2 sister chromatids seperate in

mitosis i and meiosis ii

a tetrad of 2 homologous chromosomes seperates in

meiosis i

in meiosis ii and mitosis, each side of the chromosome becomes

independent

what happens to the centromere when chromosomes seperate?

it splits

what does cohesin control?

the seperation of chromatids and chromosomes in mitosis and meiosis

cohesin is a

a protein structure, that makes a ring shape and wraps around the sister chromatids'; holding them along their arms and centromere

what happens to cohesin during anaphase?

enzyme seperase breaks up this protein

how does the enzyme seperase facilitate anaphase?

it breaks up cohesin, pullling the spindle fibers allowing the sister chromatids to seperate

how does the break down of cohesin differ in anaphase and anaphase i?

cohesin only breaks down around the arms but stays around the cnetromere

what protects cohesin from completely breaking down in anaphase i?

the protein shugoshin

why is the purpose of cohesin staying around the centromere in anaphse i?

so when the mitotic spindle fibers pull the chromosomes apart, the homologous paris stay together

in what of meiosis is shugoshin degraded?

anaphase ii

what is the result of shugoshin being degraded in anaphse ii?

all cohesin breaksdown, releasing the 2 sister chromatids from each other so they can seperate

how is genetic material introduced in meiosis?

-from crossing over between homologous chromosomes
-from the random shuffling of the maternal and paternal chromosomes

the two cells after the meiosis i both have

paternal and maternal chromosomes

why is it impossible to get a clone after meiosis?

maternal and paternal chromosomes are shuffled, always two possible alingments for any homologous pairs.

in meiosis, there are two possible orientations on the metaphase plate for every

tetrad

what is the male gametogenesis called?

spermatogenesis

what is the female gametogenesis called?

oogenesis

the testes contain a special subset of cells called

spermatogonium

the spermatogonium is a

diploid cell, the starting point of spermatogenesis

what is the cell called that is chosen to do meiosis i in spermatogenesis?

primary spermatocyte

what is the result of the primary spermatocyte going through meiosis i?

two secondary spermatocytes

what process do secondary spermatocytes go through and what is the result?

meiosis ii, 4 spermatids

when spermatids enlongate and their flagella forms they are called

sperm

what is the ploidy of both the spermatogonium and the primary spermatocyte?

2n

what is the ploidy of the secondary spermatocyte and the spermatids

1n

what is the difference between human oogenesis and other animal's oogenesis?

it does not create four gametes, an uneven cytokinesis occurs

why do human females have single births?

oogenesis only creates one ovum or egg with all of the proteins and RNA to nurture a human embryo

what are the typical products of oogenesis?

1 ovum, two polar bodies

what is the name of the cell in oogenesis that goes through meiosis i?

primary oocyte

what is the result of the primary oocyte going through meiosis i?

secondary ocyte and first polar body

what is the name of the cell that goes through meiosis ii and what is the result?

secondary oocyte, ovum and second polar body

what are the first and second polar bodies smaller than the secondary oocyte and ovum?

the uneven cytokinesis pushes all nutrients into one out of the two

what happens to the polar bodies in oogenesis

they degrade, are broken down and absorbed by the body

how many chromosomes do the polar bodies have?

23

what is the ploidy of the oogonium and primary oocyte and how many chromosomes to they contain?

2n, diploid 46

what is the ploidy of the polar bodies, and the ovum, how many chromosomes do they contain

1n, monoploid, 23

one homologous pair comes from the ____ and the other from ____

egg, sperm

the egg doesn't finish meiosis ii until it is

fertilized

chromosomes are made up of

genes

define allele

an alternative form of a gene

define gene

region of DNA that codes for a characteristic

define gentoype

written out alleles or a set of alleles possed by an individual organism

what is an example of a genotype?

RR, Rr, rr

heterozygote

two different alleles

homozygous

two of the same alleles

define phenotype

the apperance or manifestation of a character, trait

alleles seperate equally into the

gametes

Why were Mendel's experiments successful?

-garden pea can self/cross pollinate, easy to grow and 1 generation was used easier to interpret
-chose 7 visible characters with 2 contrasting forms
-developed symbols for the characters (R, r)
-did specific crosses, kept good records of all experiments

the dominant allele is what

you see in the F1 generation

Define monohybrid cross

cross involving one gene or one characteristic/trait

how did mendel cross-pollinate flowers?

cut of the stigma/female part of the flowers and then transferred the pollen with a paint brush

P generation stands for

parental generation

F1 generation stands for

filial generation, gender neutral for offspring

what cross did mendel make that defined dominant vs. recessive alleles and why?

homozygous round seeds (RR) x homozygous wrinkled seeds (rr), the F1 generation were all round. Meaning round is dominant

How did Mendel cross the F1 generation of all around seeds?

allowed them to self fertilize

What is the result of the self fertilization of all round seeds of F1 generation?

3/4 round, 1/4 wrinkle

in the F2 generation, what allele comes back/stop hiding?

the recessive allele

define particulate theory of inheritance

the recessive trait is isn't lost, it hides or overcomed by the dominant trait

Why is only one unique gamete is used for each genotype being crossed?

it would result in the same or repeated results

the dominant allele determines the

phenotype

which alleles have to show double in order to be seen in the phenotype?

homozygous recessive

by studying the patterns of pea plant inheritance, Mendel figured out

meiosis, monoploidy and diploidy

define the principle of segregation

the two members of a gene pair segregate from each other into the gametes, so half the gametes carry one member of the pair and the other half carries the other pair

the principle segregation basically describes

meiosis

the concept of dominance

in a heterozygote, only the trait from the dominant allele is observed in the phenotype

what is the result of the Rr x Rr cross?

1/4 RR, 2/4 Rr, 1/4 rr or 3/4 round and 1/4 wrinkled

what is the result of Rr x rr cross?

1/2 round, 1/2 wrinkled

what is the result of RR x RR?

RR, all around

what is the result of rr x rr?

rr, all wrinkled

what is the result of RR x Rr?

1/2 RR and 1/2 Rr, all round

what is the result of RR x rr?

Rr, all round

Name three essential structural elements of a functional eukaryotic chromosome

centromere, telomere, origin of replication

Why are the two cells produced by mitosis genetically identical?

During S phase an exact copy of each DNA molecule was created, giving rise to two sister chromatids. Mitosis ensures that each new cell receives one of the two identical sister chromatids.

Is the genetic information found in the first polar body identical with that found in the secondary oocyte? Why or why not?

No, because they are both a result of meiosis i, they contain only one member of each original chromosome pair + recombiation in prophase i

is the genetic information found in the second polar body identical with that in the ovum? Why or why not?

No, they do contain the same members of the homologous pairs of chromosome but the sister chromatids underwent recombination in prophase i