Genetics 3 Flashcards by Hannah Fairchild

occurs when chromosome fails to separate properly during meiosis

nondisjunction

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failure of one of the divisions of meiosis (I or II) to occur, producing diploid gametes

Meiotic restitution

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an organism’s genetic makeup, the heritable information stored in an individual’s genes

Genotype

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an organism’s physical traits

phenotype

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genetic and phenotypic characteristics

trait

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molecular unit of heritance, functional subunit of DNA

gene

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specific location of a gene on the chromosome

locus

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variations of genes or alternate form of a gene

alleles

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allele that always shows up

dominant

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allele that gets masked by another allele

recessive

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containing the same alleles for a gene

homozygous

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containing different alleles for a gene

heterozygous

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Involves removing anthers from a flower and introducing pollen of the desired type with a small brush

artificial cross-fertilization

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Strains that consistently produce the same phenotype

pure breeding
true-breeding
homozygous

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The trait shown by the F1 offspring

dominant phenotype

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The trait that wasn’t apparent in the F1

recessive phenotype

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Mendelian principles

Principle of segregation
Principle of independent assortment
Principle of dominance

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The two members of a gene pair segregate away from each other into separate gametes

principle of segregation

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In a heterozygote, one allele may conceal the presence of another

Principle of dominance

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Different gene pairs randomly are distributed into gametes

Principle of independent assortment

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Cross producing hundreds or thousands of progeny by repeating each cross several times

replicate crosses

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Cross in which the same genotypes are crossed, but the sexes of the parents are reversed

reciprocal crosses

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Cross unknown genotype with homozygous recessive genotype

test crosses

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numbers calculated from data that aid in analysis of said data

statistics

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used to compare data with a given hypothesis and determine if the data matches this expectation

X^2

Sex is determined by female gametes all having an X chromosome and male gametes having either an X or Y chromosome

XX/XY sex determination

Sex is determined by females having heterogametic chromosomes and males having homogametic chromosomes

ZZ/ZW sex determination

All pairs of chromosomes are the same

homogametous

All but one pair of chromosomes are the same

heterogametous

If there are two X chromosomes it's a female if it has one X chromosome it's a male

XX/XO sex determination

Males are haploid and females are diploid

Haploid-Diploid System

Genes at one or more loci determine sex, not the presence of a chromosome

Genic Sex Determination

Temperature variation controls sex determination

Environmental Sex Determination

X and Y chromosomes use these to find each other

Pseudoautosomal regions (PARs)

Non-recombining (created by only 1 strand) region

male specific region of the Y | MSY

Expresses certain traits that correlate with males

Sex-determining region (SRY)

mammal sex determination

ACTIVE-Y sex determination

targets structures in embryo that would have developed into uterus, ovaries, and fallopian tubes

Mullerian inhibiting substance

Sry is expressed normally, but receptor on X chromosome is mutated, so male with female characteristics

Androgen Insensitivity Syndrome

only have one set of alleles for every X-linked gene

hemizygous

balances the dose of X chromosome gene expression in males and females

Dosage compensation

Dosage Compensation causes

Inactivation of single X Inactivation of some genes on both X chromosomes Double expression of male genes

highly heterochromatized (condensed) X chromosome in homogametous individuals (genes are turned off)

Barr bodies

Inactivation of X chromosome is random

Lyon hypothesis

region that on chromosome that is active to make X inactive

X-inactivation center (Xic)

gene that expresses RNA that makes X inactive

X-inactive specific transcript (XIST)

disorder which causes someone to have both ovaries and testes (mosaics)

ovotesticular disorder

have rudimentary testes or ovaries

pseudohermaphrodites

degree to which a given genotype is expressed in the phenotype Eg.

expressivity | polydactyly (multiple digits)

degree to which individuals in a population express a particular trait for a given genotype Eg.

penetrance | diabetes type II

number of complete sets of chromosomes

euploid | n, 2n, 3n...

not having euploid number of chromosomes

aneuploid | 2n+1, 2n-1...

failure of homologous chromosomes or sister chromatids to separate as they normally do during cell division

Chromosome nondisjunction

2n+1

trisomic

2n-1

monosomic

people who studied gypsum weed (Datura genus)

Blakeslee and Belling

the number of copies of a gene

gene dosage

down syndrome

Trisomy 21 | 47, +21

patau syndrome

Trisomy 13 | 47, +13

edward syndrome

Trisomy 18 | 47, +18

Klinefelter syndrome

47, XXY

Jacob syndrome

47, XYY

Triple X syndrome

47, XXX

Turner syndrome

45, XO

only some of the offspring produced are viable

semisterility

having a mixture of chromosome pair combinations

Mosaicism

Have some female (XX) and some male (XO) parts

gynandromorphs

both copies of a homologous chromosome pair arise from the same parent

Uniparental disomy

both chromosome 15’s come from father

Angelman syndrome

both chromosome 15’s come from mother

Prader-willi syndrome

the presence of 3+ sets of chromosomes in nucleus

polyploidy

duplication of chromosome sets within a species

autopolyploidy

combining the chromosome sets of different species

allopolyploidy

location where both DNA strands are severed at when chromosome breaks

chromosome break point

chromosome lacking a centromere

acentric

Organisms with one normal and one terminally deleted chromosome

partial deletion heterozygotes

reattachment of broken region of chromosome in the wrong orientation

chromosome inversion

reattachment of broken region of chromosome to a nonhomologous chromosome

chromosome translocation

inversion where centromere is outside of inverted region

paracentric inversion

inversion where centromere is inside inverted region

pericentric inversion

cell with one normal and one inverted homologue

inversion heterozygotes

chromosome that results from a cross over in a paracentric inversion

dicentric chromosome

structure that results from alignment of normal chromosome and its inverted homologue

inversion loop

Cell that has one normal copy and one translocated copy | of each chromosome

Translocation heterozygotes

broken ends of nonhomologous chromosomes are reattached

translocation

a piece of one chromosome is translocated to a nonhomolog and there is no reciprocal event

unbalanced translocation

pieces of two nonhomologs switch places

Reciprocal balanced translocations

involve fusion of two nonhomologous chromosomes

Robertsonian translocations | chromosome fusions

Genes collaborate or interact to influence a phenotype

gene interaction

the gene product acquires a new function or express increased wild type activity

gain of function

The gene is hyper-functional

hypermorphic allele

The gene produces a product (usually protein) that has an entirely different function from before

neomorphic allele

non-functional gene

amorphic allele

there is a decrease in gene product

loss-of-function

partially functional gene

hypomorphic allele

heterozygous individuals display intermediate phenotypes between either homozygous type

incomplete dominance | partial dominance

heterozygotes with a different phenotype than that of either homozygote

codominance