Genetics Exam 2 Flashcards

low probability of occurrence, must be present in the last numbers

underdeveloped sex organs, breast development, large hands, and long arms and legs, low sperm count (infertile )

-wide hips (most unaware)

-caused by nondisjunction

-1 in 660 males

-only an X chromosome

-females (no Y)

-nonfunctional ovaries (infertile)

-short in stature

-caused by nondisjuction

-1 in 2000 births

the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.

-during anaphase of meiosis I or meiosis II

Do not survive

testis determining factor

-functions as transcription factor

-master switch

the presence of two or more populations of cells with different genotypes in one individual who has developed from a single fertilized egg

Inactivated X chromosome (N-1)

-XXXY = N-1→3-1= 2 barr bodies

X-inactivation specific transcript gene. only gene known to be transcribed only from inactive X chromosome

Any chromosome that is not a sex chromosome

metafemale

female

intersex

male

male

metamale

male (XY: 2A (autosomes, 1 or X and 1 for Y equals 2 autosomes or A)

-factors that cause a fly to developed into a male are NOT located on the sex chromosomes but are instead found on the autosomes.

consists of males and hermaphrodites (Testes and ovaries)

-the majority of offspring are hermaphrodites only 1% are males male x hermaphrodites = half male(X), half hermaphrodite (XX) offspring

-Lack Y chromosomes altogether, depending on the expression of the X chromosome and autosomes

temperature-dependent sex determination

enzyme that converts testosterone to estradiol or estrogen (TSD)

one chromosome extra or less but not a complete set-better tolerated in the plant kingdom-Most chromosome abnormalities are aneuoploidy

missing a chromosome (2n-1)

-embryos more likely to die, therefore trisomy more common in births. A shortage of chromosome considered more lethal

condition in which an organism has extra sets of chromosomes

-more common in plants, fish, lizards, amphibians

the correct number of chromosomes in a species

The phenomenon occurs when a person has only a single functional copy of a gene, and that single functional copy does not produce a normal phenotype. Shows a dominant pattern of inheritance.

-insufficient to provide life

-sustaining function for the organism

-3 copies of a chromosome

-produces more viable offspring than monosomy in plants and animals species

greater genetic imbalance than smaller chromosomes

A human genetic disorder resulting from the presence of an extra chromosome 21; characterized by heart and respiratory defects and varying degrees of mental retardation. 1-800 births (50 yr avg)

-20x more chance of leukemia

-Alzheimer's disease

-DSCR

-Ovum is a source mainly

chorionic villus sampling

an individual that has more than two chromosome sets that are all derived from a single species

-increase in size of organism due to larger cell size not # of cells

Extra sets of chromosomes come from different species, arise from hybridization, new chromosomes have no homologs, can create new species if followed by autopolyploidy

-need balance of genes, so tetraploids (4n) are more likely to be found in nature as an unbalance in games result in an odd number of chromosomes

Proteins are present in most but not all cells, they form complexes with Cdks and help to regulate the activities of G1/S cyclins

-suppressed when ploidy increases. stays in G1 phase due to not moving through cycle b/c of suppressed Cyclins, therefore growing larger before moving beyond the G1 phase (Auto- polyploidy)

allotetraploid where both original species are known

-Cultivated American cotton "Gossypium"

-treated with colchicine to double chromosome #, resulted in fertile amphidiploid variety of cotton, 26 pairs of chromosomes, and similar characteristics similar to cultivate variety

hybrid of wheat and rye

-increases grain production, good qualities of both species combined into hybrid

when a chromosome breaks off a part of itself and transfer it to another chromosome

-aberrations often lead to gametes that are duplicated or deficient in chromosomal regions

when the deletion involves the p or q end

deletion from the interior of the chromosome

Synapsis between chromosome with large intercalary deletion and normal complete homolog

-Requires unpaired region of normal homolog to loop out of linear structure into deletion or compensation loop

A deletion of the short arm of chromosome 5 is associated with an array of congenital malformations, the most characteristic of which is an infant cry that resembles a meowing cat.

-intellectual disability, small head, delayed development, abnormalities in the glottis and larynx leading to the cat-like crying sound

-considered a terminal deletion

-partial monosomy but best considered a segmental deletion(some or all of the p arm or short arm is missing on chromosome 5)-1 in 20k-50k births, not usually inherited

-deletion in the Telomerase reverse transcriptase (TERT) has been implicated in various phenotypic changes

chromosome segment is repeated on same chromosome

-result of unequal crossing over

-essential to the origin of new species during evolution

-New function may impart an "adaptive" advantage to organisms (over long evolutionary periods before)

-genes with duplication acquire many mutations, while sustaining its essential function.

-short period of time, the duplicated gene or the new genetic information may have no particular advantage

ex.) hemoglobin and myoglobins (DNa sequences in common, but whose gene product are distinct)

losses of nucleotide pairs in a gene

-caused by breakages or losses in chromosomes in some places

the phenomenon in which another gene with a similar function compensates for an inactive gene

narrow, slit-like eyes

-dominant X linked mutation

-caused by duplication of genes on chromosomes

differences among individuals in the number of copies of a region of the genome.

-Sometimes larger or smaller number of copies

-found in coding and non-coding regions of the genome

-5-10% of the human genome-cardiovasular disease, cancer, autism, and Type I diabetes

-greater reduction of the gene DEFB, greater chance of Crohn's disease (affects colon)

When a fragment of the chromosome is reversed

-doesn't involve lose of genetic info, but simply rearranges the linear genetic sequence

-requires two breaks along the length of the chromosome

-"sticky ends" brought close together and rejoined

inversion that does not include the centromere

inversion that includes the centromere

a loop formed by meiotic pairing of homologs in an inversion heterozygote

-could result in inversion heterozygote

the homologs will segregate, results in two normal and two inverted chromatids

abnormal chromatids are produced

chromatid with two centromeres

-during anaphase, the dicentric chromatid is pulled into two directions

-usually breaks at some point, so that part of the chromatid goes into one gamete and part into another gamete during meiotics divisions

lacking a centromere

-during anaphase, randomly moves to one pole or the other or may be lost

Exchange of genetic material between homologous chromosomes at a single locus

-occurs between two non-sister chromatids NOT between the two loci

-therefore the cross

-over is not detected because no recombinant gametes are produced

-other two chromatids of the tetrad are not involved in the exchange and enter the gamete unchanged

are defficent in genetic material,

-In fertillization, the zygote most often develope abnormally, if at all

suppresses crossing over

-due to offspring bearing crossover gametes are inviable and not recovered, possibly due to the suppression of crossing over

-inversion perpetuated within the species, therefore the cycle is repeated continuously during meiosis in future generations

-phenomenon due to crossover chromatids ending up being abnormal in genetic content

-due to the recovery of crossover products it is suppressed in inversion heterozygotes, groups of specific alleles at adjacent loci within inversion may be preserved from generation to generation

-Ghengas Kahn lineage? (Ask professor)

a chromosome containing one or more inversions that suppress crossing over with its homolog and which carries a dominant marker that is usually lethal when homozygous

-organism is heterozygous for a balancer chromosome, desired sequences of alleles are preserved during experimental work

results from the exchange of chromosome segment between 2 nonhomologous chromosomes & there is no gain or loss of genetic info

-rearrangement of genetic material

-doesn't directly alter the viability of individuals bearing it

unorthodox synapsis during meiosis

-pairing results in cross-like configuration

-genetically unbalanced gametes produced due to the unusual alignment during meiosis

are not necessarily the result of crossing over due the law of independent assortment, as the chromosome containing centromere 1 travels with either chromosomes of different centromeres

A pattern of chromosome segregation that can occur following reciprocal balanced translocation that leads to the production of viable gametes.

Leads to gametes containing duplications and deficiencies

-if participates in fertilization, lethality often occurs

-results in semisterility, plays role in evolution

-in humans results in monosomy and trisomy

Translocation in which the long arms of two acrocentric chromosomes become joined to a common centromere, resulting in a chromosome with two long arms and usually another chromosome with two short arms.

-accounts for cases of familial down syndrome which is inherited

-occurs much higher frequency over several generations "runs in families"

a parent has 14/21, D/G translocation, individual is phentotypically normal, even though they only have 45 chromosomes (carrier is unaffected)

-small region is lost from both chromosome 14 and 21 during a translocation event

-another case, parent could have 46 chromosomes, 1/4 of the time, also exhibit down syndrome

*gametes unbalanced upon fertilization = lethality occurs

Areas on chromosomes that develop distinctive breaks or gaps when cells are cultured in the absence of folic acid which is normally present in medium cultures

-regions of chromosomes that are not 'tightly coiled'

-may result in intellectual disabllity and cancer

-most fragile sites do not appear to be associated with any clinical syndrome

most commonly inherited cause of intellectual disability and occurs when a DNA series makes too many copies of itself and turns off a gene on the X chromosome

="gap region" associated with FXS, shown in picture where the arrow is pointing←

-Gene responsible is FMR1 (CGG) caused by trinucleotide repeats, also recognized in Huntington's disease and myotonic dystrophy

-in "upstream region" area adjacent to coding sequence of the gene

-individuals bearing a folate-sensitive site on the X-chromosome

-1-4000 males (all males bearing this X chromosome have it due to only have one X chromosome)

-1-8000 females (60% of females have it, due to having two X chromosomes)

-characteristics include:

→long, narrow faces

→protruding chins

→enlarged ears

-Normal human: 6 and 54 repeats

-carriers: 55 to 230 repeats

*230 + repeats = Fragile X Syndrome (FXS)

-FMR1 normal product = RNA-binding protein, FMRP known to be produced in the brain

-Absence of this protein due to inactivation caused by methylation results in intellectual disability

-linked to cancer from fragile site FRA3B on 'p' arm of chromosome 3 is often altered or missing

-FHIT - located on fragile sites, increase chance to mutations and deletions

Number of CGG repeats continues to increase in future generations

-230+ repeats exceeded, retardation becomes more severe in each successive generation as the repeats increase

-Occurs by maternal parent (mother) not the father the repeats over 230+

pairing of 3 chromosomes

the proposal that dosage compensation in mammalian females is accomplished by partially and randomly inactivating one of the two X chromosomes

occurs when different traits are inherited together more often than they would have been by chance along; it is assumed that these traits are linked on the same chromosome

-chromosomes are the are the unit of transmission not the gene during meiosis

-*linked genes are not free to undergo independent assortment

-instead transmitted as a unit

the genetic process by which one chromosome breaks off and attaches to another chromosome during reproductive cell division

-occurs during tetrad stage

linkage between genes that are located close together on the same chromosome with no crossing over between them

-exchange creates recombinant or crossover gametes

-seldom occurs between two genes

-results in all parental gamates offspring

-# of progeny is usually small

the distance separating the respective loci along the chromosome

-*The closer two genes are, the less likely there is to have chiasma form between them, therefore less genetic exchange between two genes close together

-Morgan first to propose 'crossing over' to describe physical exchange leading to recombination

the proportion of recombinant gametes increases and that of parental gametes decreases

-does not exceed 50%

-if 50 percent recombination occurs, the result is 1:1:1:1 (two parental, two recombinant gametes)

-*when genes are really close together, during meiosis or crossing over, they move as one gene, not two separate genes; However, if the genes are further apart, they are treated as two separate genes therefore increasing the likelihood of recombination because both genes are being crossed over as a separate entity and not treated as one gene.

-*expressed usually in F2 generation

-Complete linkage between two genes due to close proximity

-Unique F2 phenotypic ratio results

groups of traits that tend to appear together because they are on the same chromosome.

-# of linkage groups should correspond to the haploid number of chromosomes

X-shaped regions where crossing over occurred.

-Morgan proposed that Chiasmata could represent points of genetic exchange

-Morgan postulated that if an exchange occurs during gametic formation between mutant genes on the two X chromosomes of the F1 females, the unique phenotypes would occur

-linked genes exist in *linear order

process for determining the relative position of genes on a chromosome

-each number represents the percentage of recombinant offspring produced

female Drosophila

-occurs in both sexes in most organisms

-made genetic mapping less complex

-discovered by Sturtevant

chromosomes are carriers of genetic information and occur in linear order equivalent of Mendel's unit factors

the less likely any single

-cross over (SCO) event will occur between them

the more likely a random crossover event will occur between them

-a cross over occurs, yielding gametes

TWICE the percentage of recombinant gametes produced

-Therefore, Theoretical limit of observed recombination due to crossing over is *50%

a cross over expected to occur 100% of the tetrads

-rarely if ever happens the ratio would have to be 1:1:1:1

Exchange of genetic material between homologous chromosomes at two loci

-usually three gene pairs, each heterozygous for two alleles

-requires large # of offspring to detect a DCO when closely linked genes are involved

*DCO undetected because no rearrangments of alleles occurs

most easily recognized because they 'exist in the greatest proportion'

mapping estimates become more inaccurate

-mapping determinations usually underestimate the actual distance between two genes

*The further apart two genes are, the greater the probability that undetected cross overs will occur

-more accurate maps from experiments where genes are relatively close together

phenomenon through which a crossover event in one region of the chromosome inhibits a second event in nearby regions that causes this reduction

The more positive interference occurs

interference decreases as the genes are located further apart

Sequence variations among individuals in a specific region of DNA that are detected by molecular analysis of the DNA and can be used in genetic analysis.

-Cystic fibrosis (exocrine disorder)

variations in the DNA sequence that occur when a single nucleotide in the genome is altered

give an exact order of bases in a plasmid, chromosome, or entire genome

Reciprocal exchanges similar to crossing over

-Between sister chromatids (crossing over is between NONsisters)

-DO NOT produce new allelic combinations

-X-Rays, UV light, certain chemical mutagens) increase the frequency of SCE's

sister chromatids involved in mitotic exchanges-patch

-like appearance when stained and viewed under a microscope

The frequency of SCEs is elevated in Bloom Syndrome, caused by mutation in the BLM gene on chromosome 15.

-recessively inherited

-benign tumors, abnormal behavior patterns

-increased breaks rearrangements between nonhomologous chromosomes in addition to excessive SCEs

-BLM gene encodes for enzyme called 'DNA Helicase", which is best known for its role in DNA replication