what are the two forms of DNA
chromatin and chromosome
4 characteristics of chromatin
uncondensed DNA
replicates easily
difficult to move
difficult to see under a microscope
4 characteristics of a chromosome
condensed DNA
difficult to replicate
moves easily
easy to see under microscope
what is DNA
found in the nucleus or nuceloid of ALL cells
stores genetic information
what is cell division
dividing process cells go through to make more cells and pass on their DNA
what are the two major cell division processes
mitosis: division of somatic cells
meiosis: division of germ cells
why is meiosis so important
forms the basis for sexual reproduction
gametes produced from meiosis can be sperm, eggs, pollen, or ovules
creates genetic diversity
where does mitosis happen
somatic cells
where does meiosis happen
germ cells
what happens during mitosis
the original cell copies DNA once and divides once
what happens during meiosis
the original cell copies DNA once and divides twice
results of mitosis
2 new somatic cells each with a full set of chromosomes identical to the original
results of meiosis
4 new cells called gametes each with 1/2 the amount of chromosomes present in the original germ cell
what is diploid
2 copies of each chromosome
-human somatic cells are diploid
what is haploid
1 copy of each chromosome
-human gametes are haploid
how do you identify and count chromosomes
use the centromeres
meiosis is essential for _________
sexual reproduction
what is meiosis the basis for
genetic variation- needed for evolution to occur (gradual change in species over time)
what is genetic diversity
differences between organisms of the same species
what is crossing over
chromatids cross and exchange genetic information in equal amounts
takes place during late prophase 1
what is independent assortment
pairs of homologous chromosomes line up and separate independently of one another
-occurs at the metaphase plate
-begins during prophase 1
-continues through metaphase 1
-ends in anaphase 1
what is segregation
the separation of pairs of homologous chromosomes
-takes place during anaphase 1
name the order 1-12 of mitosis
1- pre s phase
2- early prophase 1
3- middle anaphase 1
4- late prophase 1
5- metaphase 1
6- anaphase 1
7- telophase 1
8- interkinesis
9- prophase 2
10- metaphase 2
11- anaphase 2
12- telophase 2
what is a gene
a segment of a chromosome which determines a specific inherited characteristic/trait (such as the number of humps in reebops)
what is an allele
alternate forms of genetic information for a single trait (such as M or m, for the number of humps in reebops)
-there are alternate forms, so an allele only exists as a complement to another. an allele without an alternate form somewhere in nature does no
what is locus
the actual physical area (location) on the DNA where the gene is found
what is a genotype
a collection of alleles which form the genetic make-up of an organism (MM, Mm, or mm for example)
what is a phenotype
the physical appearance of the organism (1 antenna or 2 antenna for example). the physical expression of the genotype
-it is important to realize that there is often more than one genotype that codes for a certain phenotype
what is a gamete
the haploid cell that is the end product of meiosis
what is fertilization
the actual union of two gametes, which then fuse into one cell containing the original number of chromosomes
what is a zygote
the diploid cell resulting from fertilization
what is probability
-random alignment of chromosomes during metaphase 1 and eventual distribution in the gametes
-used to calculate likelihood of certain events
what do we use chi square for
test to determine how closely the data matches our prediction
what is the point of chi square
helps us analyze the observed data
-helps us determine if the difference between what we expected to happen and what we observed was simply due to random error or some other factor is influencing the results
what is random error
natural error that happens by chance
list general steps of chi square
-use probability to determine what we expect to happen
-compare what we expected to happen to the observed data
-determine chi square value
-determine the p-value (the probability that the difference between what we expected to happen and what we observed
when there is a relatively small difference between what is expected (e) and what is observed (o) ....
we get a small chi-square and a large p-value
-this means that there is a high probability that the difference was simply due to random error
when there is a large difference between what is expected (e) and what is observed (o)....
we get a large chi-square and a small p-value
-this means that there is a low probability that the difference was due to random error
-there must have been some other factor(s) that caused the difference
why do we use models in science
-easy to access
-cheaper
-easy to manipulate
what are specific advantages of using reebops to study genetics over actual animals such as mice
-do not need to wait for each generation to reproduce
-cheaper
-scaled down genetics
-easily identifiable traits
-easier to care for
-no accidental or unplanned mating
what are some disadvantages of using reebops
-over simplified in some ways
can't replicate chromosomes, can't show crossing over
looks at one trait and the possible combinations of alleles to produce different genotypes and phenotypes for that trait
monohybrid cross
looks at two traits and the possible combinations of alleles to produce different genotypes and phenotypes for these two traits
dihybrid cross
represented by big letters, shows its effect when present in a heterozygote, it masks the effect of a recessive allele
dominant alleles
represented by small letters, only shows its effect in the phenotype when present in a homozygote, the effect is hidden when paired with dominant allele
recessive alleles
two copies of the same allele for each trait
homozygous genotype
one dominant allele and one recessive allele for each trait
heterozygous genotype
tool to look at combinations of alleles and the resulting phenotypes and genotypes
-this tool can also be used to determine what expected genotype ratios and expected phenotype rations we would likely see from a cross between individuals with given phenot
punnett square
parents
p1
children
f1
grandchildren
f2
based on outcome of punnett square for the cross between two f1 organisms
expected f2 ratio
what is the "and" rule
two simultaneous outcomes with both occurring at the same time
what is the "or" rule
either one outcome or the other outcome will occur