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Genetics test 2 study guide

by: Emmy Thornsberry

Genetics test 2 study guide BIOL 2100

Marketplace > Georgia College & State University > Biology > BIOL 2100 > Genetics test 2 study guide
Emmy Thornsberry

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These notes cover what will be on our test friday.
Yen France
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This 5 page Study Guide was uploaded by Emmy Thornsberry on Tuesday October 11, 2016. The Study Guide belongs to BIOL 2100 at Georgia College & State University taught by Yen France in Fall. Since its upload, it has received 31 views. For similar materials see /class/221936/biol-2100-georgia-college-state-university in Biology at Georgia College & State University.


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Date Created: 10/11/16
Genetics Test 2 Study Guide Chapter 7 Linked Genes - Linkage- genes close together on the same chromosome tend to stay together during the formation of gametes and generally do not follow the laws of independent assortment - Ratios- AaBb x aabb in linked genes is a 1:1 ratio - AaBb x aabb in recombinant genes is 1:1:1:1 - Linkage with some crossing over leads to <50% recombinant/ >50% nonrecombinant - Linkage and crossing over - Linkage can be altered during meiosis due to crossing over- non sister chromatids exchange DNA - No crossing over- 4 nonrecombinant gametes - Crossing over- 2 nonrecombinant, 2 recombinant gametes - Recombination Frequency=(recombinant/total)x100 Mapping Chromosomes - Determining linkage - Map units are the % of the time that linkage occurs, as well as the unit of measurement to determine distance apart. - If two genes’ loci are more than 50 map units apart, they are not linked - Counting recombinant events determines map units - Example. AaBb female mates with aabb male. The distance between A and B on the female chromosome is 20 map units. Solution: Determine the offspring of both. Male offspring will be 100% recessive because they are heterozygous. Female offspring will be 80% nonrecombinant and 20% recombinant due to the distance between A and B. Cross the offspring of male and female and take the ratios of the female offspring. A B ​ ​Offspring of Female ​ ​Offspring of male​ ​Offspring a b AB=40% ab=100% AaBb=40% ab=40% aabb=40% Ab=10% Aabb= 10% aB=10% aaBb=10% - Three point crosses - Steps to solving - 1. Pair offspring - 2. Determine nonrecombinant offspring - 3. Determine double cross - 4. Determine order of loci - 5. Rewrite in correct order - 6. Determine configuration - 7. Calculate single and double cross values (offspring/total) - 8. Add single cross and double cross to calculate map units Coupling and Repulsion Configuration of Linked Genes - Coupling- cis configuration; one chromosome contains both wild types, the other contains both mutant types - Repulsion- trans configuration; each chromosome contains one wild and one mutant - Cis and trans produce the same offspring but in different ratios - Cis- more nonrecombinant than recombinant - Trans- more recombinant than nonrecombinant Chapter 25 Population genetics - Genetic structures of populations - Focus on phenotype, genotype and alleles - Focus highly on alleles because they determine genotype and phenotype - Looks at patterns of genetic variance in populations - Changes in genetic structure through time - Frequencies - Genotype - f(AA)=AA/total - f(Aa)=Aa/total - f(aa)=aa/total - Allele - f(A)=(2AA+Aa)/2(total) - f(a)=(2aa+Aa)/2(total) - q= recessive allele=f(aa)+1/2f(Aa) - p=dominant allele=f(AA)+1/2f(Aa) - p+q=1 - Gene pool- all alleles present for genes of a population - Hardy Weinberg Equation - Describes the allele and genotype frequencies of a population at equilibrium - p​ +2pq+q​ =1​ - Assumption - Population is large, randomly mating, not affected by mutation, migration, or natural selection - Predictions - Allele frequencies of populations do not change - Genotype frequencies stabilize - Dominant and recessive cannot be determined by frequencies - Non random mating - Inbreeding - Increases proportion of homozygotes - Decreases the proportion of heterozygotes - Allele frequency doesn’t change, just distribution - Results in lethal alleles, disease, etc that only show in homozygous state - Inbreeding depression- decrease in diversity from loss of heterozygotes - Outbreeding- breeding outside of family - Vocab - Positive assortative mating- tendency of like individuals to mate - Negative assortative mating- tendency of unlike individuals to mate - Inbreeding coefficient- offspring are 50% like each parent, 25% like each sibling, etc. can be calculated by multiplying the proportional differences aka sibliing A is 50% parent x 50% parent= 25% sibling B - Evolution force causes changes of allele frequency - Mutation- ultimate source of genetic variation, appearance of new allele changes frequency - Migration- movement of individuals, takes away a portion of diversity to change allele frequency - Genetic drift- changes probability of allele distribution and genetic variation - Selection- one trait that is more favorable than another will result in a shift in alleles toward one trait - Same populations - Mutation- increase variation - Migration- increase variation - Genetic drift- decrease variation - Selection- can increase or decrease - Between different population - Mutation- increase variation - Migration- decrease variation - Genetic drift- increase variaion - Selection- can increase or decrease Chapter 8 Chromosome structure and variation - Karyotyping - Chromosomes prepared from metaphase of actively dividing cells then arranged according to size - Mutations - Aneuploids-trisomy due to nondisjunction - Polyploids- autotriploid, extra set of chromosomes - Chromosomal rearrangement - Duplication - Causes imbalance in gene products, tandem repeats(side by side repeats), displaced repeats (repeated and placed somewhere else, or reverse repeats(repeats sequence in reverse order) - Caused by: one segment of the sequence gets duplicated and leads to unequal crossing over, chromosomes do not line up evenly and cause a duplication - Deletions - Causes no assortment if the centromere is included, homozygous lethality because there is no backup copy, recessive traits, and dosage imbalances if something necessary is deleted - Inversions - Replicated but flipped - Homozygous in meiosis- makes no difference - Heterozygous in meiosis- - Homologous sequences align only if they form an inversion loop - Reduced recombination in paracentric inversions because gametes formed result in nonviable offspring - Have abnormal gametes formed in pericentric inversion - Paracentric - Not including centromere - Must form loop to help align loci - Reduced recombination among genes - Dicentric- 2 centromeres - Acentric - no centromeres - Recombinant gametes lack many genes and are not viable- no recombinant gametes - Pericentric - Includes centromere - Form inversion loop - Reduced recombination because recombinant gametes either have too many or not enough copies and are nonviable - Translocations - Movement of genetic material between two nonhomologous chromosomes or within the same chromosome - Two non homologous chromosomes swap pieces of their chromosomes - Reciprocal translocation - Evenly traded genetic material - Nonreciprocal translocation - Taken genetic material- goes from one chromosome to another - Robertsonian translocation - Two breaking points result in one large and one very small chromosome which is usually lost - Meiosis - Causes chromosomal alignment outside of homologous pairs due to the genetic material in differing chromosomes - Adjacent segregation produces nonviable offspring because not all necessary genes are present - Alternate segregation produces viable offspring because all necessary genes are present Changes in chromosome number - Variations in copy number cause polyploidy and aneuploidy - Aneuploidy types - Nullisomy- loss of both members of a homologous pair (2n-2) - Monosomy- loss of one chromosome (2n-1) - Trisomy- gain of one chromosome (2n+1) - Tetrasomy- gain of two chromosomes (2n+2) - Effects of aneuploidy - Typically lethal - Abnormal gene dosage - Sex chromosome aneuploids- Turner syndrome, Klinefelters, poly-x - Autosomal aneuploids - Small autosomes allow for nonlethal situations (Downs syndrome) because the chromosome is small - Primary Downs- nondisjunction in eggs - Familial Downs- Robertsonian translocation between chromosomes 14 and 21- leads to only one chromosome 21 because the other is attached to 14 - Alloploidy - Hybridization of two species - Happens often in plants


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