Chapter 11

the study of heredity

genetics

an organism has a homozygous genotype. Its gametes always receive the same allele for a trait. Plants self pollinate

true-breeding

a characteristic of an organism

trait

individual has a heterozygous genotype. It parents had different true-breeding phenotypes for the trait.

hybrid

means the same as homozygous for a trait

purebred

segment of the dna that codes for a protein/trait

gene

alternative form of a gene

allele

alleles separate during gamete formation

segregation

sex cells (haploid)

gamete

the likelihood that an event will occur

probability

both of an individual's alleles for a trait are the same

homozygous

each of an individuals' alleles for a trait are different. Its gametes may receive 1 allele of the other

heterozygous

the trait expressed from the genotype, the physical expression of the genotype

phenotype

the alleles that an organism has. This will determine the phenotype

genotype

genes for different traits can segregate independently during gamete formation.

independent assortment

both alleles contribute to the phenotype (black feathers and white feathers on a chicken)

codominance

genes that have more than 2 alleles within the population (an individual can still only possess 2 alleles)

multiple alleles

cases in which one allele is not completely dominant over another resulting in a phenotype that is somewhere between the two in the hybrids (looks like blending occurred in heterozygous individuals)

incomplete dominance

traits produced by the interaction of 2 or more genes (produces many different phenotypes)

polygenic traits

organisms that have two identical alleles for a trait (ex. TT or tt)

homologous

(genetics) an organism or cell having two sets of chromosomes or twice the haploid number

diploid

one set of chromosomes as in gametes

haploid

a process of reduction division to create haploid sex cells.

meiosis

when homologous chromosomes exchange portions of chromatids during meiosis 1

crossing over

four chromatids in a pair of homologous chromosomes

tetrad

term that means an organism has two identical alleles for a trait

homozygous (pure breed)

term for a trait with different alleles

heterozygous (hybrid)

what is the difference between codominance and incomplete dominance?

codominance-both are present (Dalmatian)
incomplete dominance- is a mixture of both (pink flower from red and white)

what does polygenic mean?

many genes

what is an example of a polygenic trait in humans?

human eye color

what is the difference between diploid and haploid?

diploid- is homologous chromosomes, body/somatic cells.
haploid- is half the number of chromosomes, sex cells/gametes.

what is crossing over?

when the little part of a chromatid changes, all the chromosome different, from a tetrad

during what phase and what process does crossing over occur?

prophase 1/ meiosis

what is the difference between hybrid and pure breeds?

prue breeds both TT or tt, hybrids Tt.

what are Mendel's four basic principles. Briefly describe each.

1. Inheritance is determined by factor/genes. --Passed from parent to offspring.
2. Law of Dominance.-- Some alleles are dominant, some are recessive.
3. Law of segregation.-- Alleles separate during gamete formation. T/t
4. Law of independent assortment.

what assorts independently during "independent assortment?

blue eyes do not always mean blond hair.

what is the probability of tails coming up in a coin toss?

1:2

How do geneticists use the principle of probability?

by the punett square; predict possible

If a haploid number of chromosomes in an organism is 18 what is its diploid number?

36

If the diploid number of an organism is 20, what is its haploid number?

10

how many alleles for each gene are found in gametes? and in somatic cells?

gametes: 1 and somatic cells: 2

What do mitosis and meiosis have in common- both begin with dna ____;both start with _____ cells; both produce more ______.

replication; diploid; cells

In what four ways are mitosis and meiosis different? The purpose of mitosis is to produce ___/___ cells where as the purpose of meiosis is to produce ___/____ cells. Mitosis results in __(#) ______ cells where as meiosis results in __(#) ____ cells. The c

body/somatic; gametes/sex; 2; diploid; 4; haploid; same; different; crossing; divide; 1

during oogenesis, the 3 smaller cells produced are called ____ _____ and are not ______. The larger cell is the ____ and is viable.

polar bodies; viable; ovum

In males, the specific type of gametogenesis that occurs is called ___.

spermogenesis.

what is the phenotypic ratio did Mendel come up with in his F2 generation of the dihybird cross?

9:3:3:1

different forms of a gene are called?

alleles

if a tall homozygous pea plant and a homozygous short pea plant are crossed?

the recessive trait seems to disappear.

A punnett square is used to determine the?

probable outcome of a cross.

organisms that have two identical alleles for a particular trait are said to be?

homozygous

the physical characteristics of an organism are its

phenotype

a situation in which a gene has more than two alleles is known as

multiple alleles

unlike mitosis, meiosis in male mammals result in the formation of

four haploid gamete cells

to maintain the chromosome number of an organism, the gametes must

be produced by meiosis.

what happens to the chromosome number during meiosis?

it doubles

which ratio did Mendel find in his F2 generation?

3:1

During which phase of meiosis is the chromosome number reduced?

telophase 2

two pink-flowering plants are crossed. The offspring flow as follows: 25% red, 25% white, 50% pink. What pattern of inheritance does flower color in these flowers follow?

incomplete dominance

Alleles for the same trait are separate from each other during the process of?

meiosis 1

Which of the following is not one of Gregor Mendel's principles?

Crossing over occurs at meiosis.

offspring of crosses between parents with different traits.

hybrids

appearance due to genetic make up

phenotype

having two identical alleles for a given gene

homozygous