AP BIO Unit 5 Test Review

What are homologous chromosomes?

Two chromosomes with the same set of genes, sometimes with different alleles

What is a gene?

basic unit of heredity and a sequence of nucleotides in DNA or RNA

What is an allele?

Different forms of a gene

Purpose of meiosis

produce gametes

Why in meiosis the chromosome number is halved?

Halves the sex cells in half, so that in fertilization, it will result in a normal amount of chromosomes (46 -\> 23)

What is the end product of meiosis?

4 haploid cells

stages of meiosis in order

Interphase, Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II

What happens in meiosis I?

• Homologous chromosomes pair up

• Homologous chromosomes separates

• Two haploid cells are made with their sister chromatids still joined.

What happens in meiosis II?

• Sister chromatids separate

• 4 haploid daughter cells are formed

Significance of meiosis

Causes genetic variation

How is genetic variation achieved?

• crossing over

• independent assortment

• random fertilization

• mutations

What is crossing over?

exchange of genetic material between homologous chromosomes

How does crossing over contribute to genetic variation?

Crossing over creates new combinations of genes in the gametes that are not found in either parent

What is independent assortment ?

random separation of homologous chromosomes

How does independent assortment contribute to genetic variation?

each gamete ends up with a different set of DNA

* independent assortment affects which chromosomes end up in each cell

How does random fertilization contribute to genetic variation?

each parent to randomly contributes a unique set of genes to a zygote

What is a recessive allele?

A form of a gene that is not expressed when paired with a dominant allele

What is a dominant allele?

A form of a gene that is fully expressed, even when two different alleles are present

What is the law of segregation?

Parents pass on only one allele for each gene

What is the law of independent assortment?

during gamete formation, different pairs of alleles segregate independently of each other

• EX. which allele a gamete receives for gene A has no bearing of which allele a gamete receives for gene B

• ONLY DEALS WITH UNLINKED GENES

What are unlinked genes?

genes located on different chromosomes

What are linked genes?

genes located on the same chromosome that tend to be inherited together

What is a punnett square?

A chart that shows all the possible combinations of alleles that can result from a genetic cross

What is a dihybrid cross?

a cross that examines the inheritance of two different traits

What is the probability rule regarding multiplication?

Independent events that occur in a sequence; "AND"

What is the probability rule regarding addition?

Events not happening in a sequence; "OR"

What is incomplete dominance?

when one allele is not completely dominant over the other; blending of traits from parents (red+white\=pink)

What is codominance?

both alleles contribute to the phenotype

How does the environment affect phenotype?

Exposure to certain things in the environment can affect gene expression and what phenotype is displayed.

What is a pedigree?

a chart that tracks which members of a family have a particular trait

What is autosomal recessive?

no skipping, many affect; two recessive needs to be present in order for the disease or trait to develop.

What is autosomal dominant?

Dominant in a trait that is not directly involved in determining sex; no skipping and many affected

What are sex-linked traits?

Traits controlled by genes located on sex chromosomes.

What is X-linked recessive?

mother/son and father/daughter links, skipping of gen

What is x linked dominant?

• Expressed in female in one copy

• more males affected

What is mitochondrial inheritance?

trait inherited from the moms and passes down to all kids

What is a genetic map?

ordered list of the genetic loci along a particular chromosome

What is nondisjunction?

Failure for chromosomes to separate properly.

What can nondisjunction lead to?

genetic abnormalities and chromosomal disorders

Name the 5 altercations of chromosome structure (mutations).

• deletion

• insertion

• duplication

• translocation

• inversion

What is a deletion mutation?

one nucleotide is taken away from a gene or DNA sequence

What is an insertion mutation?

The addition of a single nucleotide

What is a duplication mutation?

repeats a segment

What is an inversion mutation?

Reverses a segment within a chromosome

* BDE -> BED

What is a translocation mutation?

moves a segment from one chromosome to another, nonhomologous one

What type of chromosomal mutation is least disruptive?

point mutation because one base pair is exchanged and frame shift does not occur

What does mitosis produce?

2 identical diploid cells

What does meiosis produce?

4 differing haploid cells

What does meiosis result in?

daughter cells with half the number of chromosomes as the parent cell

What happens in anaphase II?

sister chromatids separate

Where does crossing over occur?

prophase I

Where does random assortment occur?

metaphase I

These chromosomes possess the same structure and genes, but are not identical. They contain different alleles for the same genes. Offspring receive one from each parent.

homologous chromosomes

Name the pattern of inheritance: males primarily affected. Women are typically carriers because they have 2 X chromosomes. Fathers cannot pass on to sons.

x linked recessive

once you solve for chi square to make meaning of your calculation, what is your next step?

determine the degrees of freedom

The closer two linked genes are on a chromosome, the ______ likely they are to be separated by crossing over?

less

the environment can change the ________ of an organism

phenotype

Choose the correct genotype for two traits of a recessive individual in a pure breeding parent generation

aabb

a type of mutation where chromosomes do not separate properly during meiosis

nondisjunctional

Diploid number is 50, what is haploid number?

25

process by which sexually reproducing organisms produce genetically diverse haploid gamates?

meiosis

crossing over results in…

recombinant chromatids

Name the inheritance pattern: affected mothers with all affected children

mitochondrial

two genes on the same chromosomes have a recombination frequency of 25%. How many map units are they apart from each other?

25 map units

How many cell divisions are in meiosis?

2

During crossing over ________ exchange genetic information

non sister chromatids of homologous chromosomes

Name the pattern of inheritance: unaffected parents have affected offspring

autosomal recessive

Chromosomes moving to opposite ends of the cell during anaphase takes place during….

both mitosis and meiosis

Due to light level changes in the environments, an arctic hare’s fur changes from white to brown depending on the season. How has the hare changed?

the phenotype changed

T/F Homologous chromosomes separate during anaphase I

TRUE

Mutations during _______ can be passed on to offspring

meiosis

Chi square vale is 6.2. Critical value is 7.81.

fail to reject the null. results are due by chance, the chi square value is less than the critical

3 ways meiosis contributes to genetic diversity

fertilization, crossing over, random assortment

reproduction that does not require the production and fusion of gametes?

asexual reproduction

a benefit of sexual reproduction

increases genetic diversity

Choose the correct genotype for an individual who is homozygous dominant for two traits

AABB

Chromosomes lining up in the middle of the cell takes place in….

both mitosis and meiosis

T/F When genes are linked the majority of the phenotypes of the offspring will resemble the phenotypes of the parents

TRUE