Genetics Exam 1

Gregor Mendel

first person to systematically study heredity using pea plants, starting with pure breeds (TT, tt, PP, etc.)

heredity

the tendency for traits to be passed down from parent to child

monohybrid

a cross with one characteristic and dominant and/or recessive traits

genotype

the genetic makeup of an allele

phenotype

the physical expression of the genetic makeup

alleles

alternate forms of a single gene

particulate

contrast with blending

Mendel’s 1st law (of segregation)

two copies of a gene separate from each other during transmission of parent to offspring

Mendel’s 2nd law (of independent assortment)

Two different genes will randomly assort their alleles during the formation of haploid cells

dihybrid cross

a cross between two different characteristics

haploid

genes cannot move independently of the other genes on the same chromosome in a dihybrid cross (linked assortment)

independent assortment

dihybrid assortment were genes can move without restriction.

test cross

allows geneticist to determine the genotype by crossing to a homozygous recessive specimen.

autosomal

trait not on the sex chromosome, therefore males and females are affected equally

recessive

alleles/diseases that often skip generations

dominant

alleles/diseases that cannot skip generation

23

humans have __ pairs of chromosomes

46

humans have __ chromosomes in total

sister chromatids

after replication, each chromosome consists of two identical _____

centromere

spot where two sister chromatids are joined, equals the number of chromosomes

kinetochore

protein complex that allows attachment of chromosomes to spindle fibers in cell division

telomere

the ends of the chromosome

homologs

pairs of chromosome that you inherit from each parent during fertilization

G1

phase where cell mass increases in preparation for the next phase

S

synthesis phase where DNA is replicated, chromosomes are duplicated, and sister chromatids are formed

M

phase where mitosis occurs

polar

microtubules that do not grab onto

kinetochore

microtubules that hit the kinetochore and attach to it

aster

microtubules that anchor the whole apperatus

interphase

state of the cell in stages G1, S, G2

prophase

stage when the two centrosomes move to opposite poles of the cells, chromosomes become condensed, and sister chromatids become visible

prometaphase

stage where chromosomes are clearly double structure, centrioles reach opposite poles, and spindles start to form

metaphase

stage where centromeres align in the middle of the cell

anaphase

stage where the chromosomes are pulled apart

telophase

stage where daughter chromosomes arrive at the poles and cytokineses commences

cytokineses

the dividing of the cytoplasm

gametes

meiosis results in the formation of _____

reductive

the division where gametes end up with half the number of chromosomes that the parent has (meiosis I)

independent assortment

produces new genetic combination between chromosomes

leptotene

part of prophase I where chromosomes condense

zygotene

part of prophase I where the homologous chromosomes find each other and the “zipper” is started

pachytene

part of prophase I where the chromosomes are totally zipped up and crossing over occurs

diplotene

part of prophase I where chromosomes start unzipping

diakineses

part of prophase I where chromosomes are unzipped and held together by crossing over

crossing over

produces new genetic combinations within chromosomes

fertilization

produces new genetic combinations between individuals

mitosis

somatic cells, 1 round of division, no aligning at equator, chromys seperate at centromere, diploid, genetically identical

meiosis

germ cells, 2 rounds of division, aligning at equator, chromys seperate at centromere, haploid, genetically unique

probability

the chance that an event will occur, (= number of times an event occurs/total events)

the sum rule

the probability that one of two or more mutually exclusive events will occur is equal to the sum of the individual possibilities

Mendelian inheritance

inheritance patterns that follow Mendel’s two laws (not related to sex, environment, level of protein expression

genetic polymorphism

when species have more than one phenotype in a wild population

gain of function mutation

new or abnormal function

dominant negative mutation

mutant protein counteracts the normal protein, most often occurs in cases where the gene product functions as part of a dimer

recessive mutation

usually leads to a loss of function which is masked if a normal copy of the gene is present

dominant mutation

lead to mutant phenotypes in the presence of a normal copy of the gene, resulting often in a gain of function

loss of function mutation

either reduce of abolish the functional activity of the gene product

incomplete dominance

heterozygote that exhibits a phenotype in between the two parents

incomplete penetrance

when a dominant genes are not expressed, does not “penetrate” into the phenotype

expressivity

the degree to which a trait is shown

norm of reaction

phenotype range observed ion individuals with a certain genotype

heterozygote advantage/overdominance

when the heterozygous individuals are more vigorous than either of the corresponding homozygotes (such as sickle cell anemia)

codominance

when two different alleles are not dominant over each other, such as in blood

x-linked

mostly males are affected; females are often carriers

sex-linked

refers to case where alleles are dominant in one sex but not the other (pattern baldness)

lethal alleles

where an individual dies as a result of certain alleles, may disrupt normal medelian ratio

sex-limited

case where a trait can only occur in one sex

pleiotrophy

the multiple effects of a single gene on the phenotype of an organism

gene redundancy

case where one gene compensates for the loss in function of another

epigenetic inheritance

when a gene.chromosome shaws altered expression but the modification is not permanent over generations

extranuclear inheritance

involving genes that are found outside the nucleus (mitochondria) where all genes come from the mother

dosage compensation

offsets the doubled amount of gene expression that would otherwise occur in one sex more than another

gene interaction

occur when two or more genes influence the outcome of a single trait

genomic imprinting

process of silencing genes via methylation

epistasis

when the alleles of one gene mask the phenotype effect of the alleles in another gene

complimentation

when two mutants with the same mutant phenotype mate together to get wild type offspring, meaning the mutations occur in different genes

prader-willi syndrome

disease caused by deletion of genes on chromosome 15 from dad

angelman syndrome

disease caused by deletion of genes on chromosome 15 from mom

mitochondrial

diseases that can be caused by 1. mother to offspring via cytoplasm of egg 2. accumulation of mutations in somatic cells

population genetics

aims to understand genetic composition of a population and forces that change that composition over time

polymorphism

“many forms” traits that display a variation within a population

population

group of interbreeding individuals of the came species in the same region

gene pool

all of the alleles of every gene in the population

gene flow

sharing of DNA within a population

microevolution

changes in the allele frequencies over time

mutation

spontaneous change in the DNA

migration

individuals moving into a population, introducing new alleles

natural selection

differences in survival and reproduction that causes an allele to become more common

directional selection

natural selection for one phenotype over the other, causing a shift in the allele frequencies

stabilizing selection

natural selection causing an allele shift to the middle of two traits (quantitative, determined by multiple genes)

disruptive selection

natural selection causing a allele shift against the middle of two traits (favors polymorphism)

genetic drift

genetic change by chance alone, has the biggest effects on small populations

bottleneck effect

reduced genetic variability following some large disturbance that removes a large portion of the populations

founder effect

reduced genetic variability following isolation of certain alleles from the original population

positive assortive mating

when individuals chose mates that are genetically more like themselves

negative assortative mating

when individuals chose mates that are genetically unique to themselves

exam review

ABOUT EXAM

33 Qs

do NOT need to know diseases (EXCEPT inheritance of blood type, Prader Willi & Angelmann’s, sickle cell anemia)

Study guide on canvas

Mendelian laws and allele inheritance all fair game