Bio105 Final exam

allele is a

variant of a gene= characteristics

regulatory region

helps decide when genes turn on or how much they’re turned on

homozygous

alleles are the same

heterozygous

alleles are different

phenotype

color/appearance

law of segregation

homologous chromosomes separate, leading to each gamete contains a single allele

the law of independent assortment

Alleles of different genes separate independently during gamete formation, so inheritance of one trait usually does not affect another trait

crossing over adds

new allele combinations to each chromosomes in prophase 1

what chromosome has SRY gene

Y chromosome has SRY gene

SRY gene confers

maleness, forms testses, testosterone production

absence of SRY gene results in

ovary formation

XX genotypes with an added SRY gene result in

male offspring

X chromosome has more

genes compared to the y chromosome

for recessive traits

two copies of affected allele are needed

dominant traits

single copy of the affected allele is needed

Sickle cell anemia

homozygous recessive (ss)

Non-Mendelian: incomplete dominance

• One allele is not dominant over another

• a mix of both alleles, like white plus red flower = a pink flower

Non-Mendelian: co dominance

• both traits expressed

• both phenotypes shown with heterozygous allele

• ex. white AND red will show

polygenic

• multiple genes affect blood type

O blood type is

recessive and A and B are co dominant

ABO system

• → A, B, AB, O blood types

Rh system

→ + or − (this is the Rh factor). RR or Rr is plus

if wrong blood is donated to a body

immune system will recognize blood as foreign and attack them

Epistasis

One gene masks or modifies the expression of another gene.

ex. albinism, lack of pigmentation masks pigmentation

Can the environment impact expression of genes

yes

crossing over occurs in

prophase 1

hemophilia is

X linked recessive meaning: Xh is affected

porcupine man

on Y chromosome- recessive

sickle cell anemia

homozygous recessive, red blood cells become sick, decreasing the ability to carry oxygen but Ss and ss help prevent malaria

achondroplasia (dwarfism)

homozygous dominant —> AA no live birth Aa dwarfism, aa normal

for blood type Rh+ comes from

RR or Rr

for blood type Rh - comes from

rr

What is epistasis? (Blood type example)

One gene affects another gene’s expression.

In blood typing, hh blocks the H protein, so IA, IB, and i can’t be expressed properly.

blood type is polygenic because

multiple genes factor in, including: Rh, H and ABO

Pleiotropy

One gene affects multiple phenotypes

ex. Sickle cell anemia affects multiple organ systems

genotype

internal genetic code or letters

complex trait

A trait influenced by multiple genes and often environmental factors.

Continuous trait

has range of variation like height or skin color.

Dominant

An allele that is expressed when at least one copy is present.

Multiple alleles

gene has 2+ possible alleles in a population (e.g., ABO blood type).

Recessive

An allele that is only expressed when two copies are present.

Sex-linked trait

A trait controlled by genes on sex chromosomes (usually X chromosome).