BIOL 350 - Principles of Genetics Exam 2

KU summer 2025

particulate theory of inheritance

the genetic determinants that govern traits are inherited as discrete units that remain unchanged when passed from parent to offspring

Mendel’s Law of Segregation

during gametic formation, the paired factors segregate randoms so that half of the gametes receive one factor and vice versa

loss of function alleles are often _____

recessive

Features of autosomal dominant disease pedigrees (Aa & AA are affected)

1. sexes equally affected

2. every affected person has affected parent

3. half the offspring of affected person are affected

features of autosomal recessive disease pedigrees (aa affected)

1. sexes equally affected

2. affected person typically have unaffected offspring

3. most affected people dont have affected parents (usually carrier parents)

4. 1/4th offspring of two heterozygous parents are affected

human homogametic sex is (diploid/haploid) for x-linked genes

diploid

human heterogametic sex is (diploid/haploid) for x-linked genes

haploid

Why are x-linked disease much more common in the homogametic sex (XY)?

only need one X chromosome to have the disease to be affected, while XX needs both X chromosome to be affected

features of x-chromosome inheritance

1. XX females transmit each x-linked allele to ½ sons and ½ daughters

2. in females, X behaves like an autosome

3. XY males are hemizygous for X

4. XY males with x linked recessive allele will express the recessive phenotype

5. XY males pass X to all daughters and no son

X-linked recessive disease features (xx and xY are affected)

1. affected individuals are likely male; highly unlikely to have affected female

2. affected males will have unaffected sons and carrier daughters

3. carrier females will have a 1:1 ratio of normal and affected sons

X-linked donimant disease features (XY and Xx are affected)

affected males pass disease to daughters only

How are homologous pairs identical

1. size

2. banding pattern

3. centromere location

4. same genes (diff alleles tho)

X & Y sex chromosomes (are/are not) homologous

are not

Prokaryotic mode of reproduction (not just asexual)

binary fission

What protein recruits the creation of a new cell wall in prokaryotes

FtsZ protein

Five phases of mitosis in eukaryotes

1. prophase

2. prometaphase

3. metaphase

4. anaphase

5. telophase

4 things that happen during Prophase

1. nuclear envelope dissociates

2. chromatids condense

3. centrosomes separate

4. mitotic spindle apparatus forms

3 types of microtubules in mitotic spindle apparatus

1. aster

2. polar

3. kinetochore

1 thing that happens during Metaphase

dyads line up at middle of cell

3 things that happen during Anaphase of mitosis

1. connection holding sister chromatids is broken so each chromatid is linked to a single pole

2. kinetochores shorten and pull chromatids to poles

3. polar microtubules lengthen and push the poles apart

2 things that happen during Telophase of mitosis

1. chromosomes reach the poles and decondense

2. nuclear membrane reforms at each pole

Different structure formed during cytokinesis in animals and plants

animals: cleavage furrow

plants: cell plate

Outcome of mitotic cell division

2 daughter cells with same chromosome number and genetically identical to mother cell

How do the products of meiosis differ from mitosis (2 main things)

mitosis 2 genetically identical diploid cells

meiosis 4 not identical haploid cells

Why are the 1n products of meiosis not identical to one another?

Only one homolog from each pair of chromosomes in a single 1n cell. each homolog has diff alleles many diff combinations of the 23 single homologs

products of Spermatogenesis

4 haploid sperm cells

what is an acrosome in sperm cells

digestice enzyme allowing penetration of the protective layers of an oocyte

Oogenesis

1. early in embryonic development: diploid oogonia produce diploid primary oocytes

2. primary oocytes initiate meiosis 1 then halt in prophase and become dormant until sexual maturity

3. puberty primary oocyte activated periodically and produces second polar body and secondary oocyte

4. secondary oocyte is released and goes through meiosis 2 if fertilized by sperm

wild-type allele (rare or prevalent)

prevalent alleles in a population

wild type alleles typically encode proteins that (2 things)

1. function normally

2. made in proper amounts

genetic polymorphism

more than one wild type in large populations

mutant alleles (rare or prevalent)

rare in natural populations

mutant alleles typically encode proteins that (2 things)

1. are defective in their ability to express a functional protein

2. are inherited in a recessive fashion

2 ways that heterozygous genotype does not change phenotype when mutant is recessive

1. 50% of the functional protein is sufficient to accomplish cellular function

2. normal gene is up-regulated to compensate for nonfunctioning allele

dominant mutations are (more/less) common than recessive mutations

less

Three types of dominant allele mutations

1. gain of function

2. mutant acts antagonistically to normal protein

3. haploinsufficiency

haploinsufficiency

recessive allele in heterozygote does not make enough functional protein to accomplish its cellular function

incomplete penetrance

heterozygote sometimes doesn’t express the trait caused by the dominant allele

expressivity

degree to which trait is expressed

incomplete dominance

heterozygote exhibits intermediate phenotype of the homozygotes

multiple alleles

more than 2 alleles for a single gene

multiple alleles are (rare/common) in natural populations

common

pleiotropy

gene with multiple effects

most genes (are/are not) pleiotropic

are

3 ways a gene can be pleiotropic

1. product can affect cell in multiple ways

2. gene expressed in diff cell types

3. gene expressed at diff stages of development

gene interactions

2 or more genes influence the outcome of a single trait

complementation

same mutant phenotype is produced by mutations in different genes or unique mutations in the same genee

epistasis

a gene can mask the phenotypic effects of another gene

why does epistasis commonly occur

the proteins participate in a common pathway and both are needed to produce phenotypic effects

complementation tests: complementation result

cross results in F1 with wildtype phenotype

complementation tests: noncomplementation result

cross results in F1 with mutant phenotype

maternal effect is an inheritance pattern in which _____ determines the phenotype of offspring

only the mother’s genotype