Midterm 1 Flashcards
What is a trait?
any observable characteristic of an individual
what is a phenotype?
observed category of measured level of performance for a trait in an individual ex. red coat color
genotype
genetic makeup of individual, constists of mom and dad contribution for everytrait
crossbreeding
mating animals from different breeds
heterosis
superiority of an outbred individual related to the average performance of populations (hybrid offpsring has imporved traits)
inbreeding
mating of closely related individuals
pure breeding
mating individual within the same breed- maintain bloodlines and pedigrees
*dominance
heterozygote is identical to expression of homozygous genotype
- pheonotypically no difference
-prone to genetic disease
*partial dominance
heterozygote is intermediate to expressions of homozygous genotypes, more closely resembles expression of homozygous dom. genotype
*no dominance
heterozygote is exactly midway between expressions of homozygous genotypes
enviornment effects
external effect factors (non-genetic) have on an animals performance
relationship with each other
phenotype= genotype+enviornment
homozygous
when both genes at a locus are functionally the same (AA or aa)
heterozygous
when both genes are at a locus are functionally different (Aa)
Gene
physical unit of heredity consisting of DNA sequence on chromosome
DNA
heredity material in humans and all other organisms
chromosome
long strand of DNA and associated proteins present in the nucleus of a cell
locus
location of gene on chromosome
allele
alternative form of gene, must be functionally different
-upper letter = most dom and listed first
mitosis
creates exact copy of parent cells
- starts and ends w same # of chromosomes
meosis
occurs in reproductive/germ cells (ovary and testies) leads to formation of Haploid cells
mitosis vs meiosis
meiosis has 2 divisions (meiosis 1 and 2)
prophase 1 (meiosis 1)
crossing over- physical exchange of chromosome pieces
- each daughter cell contains 1 pair of sister chromatids
meiosis II
- no crossing over
-4 haploid spermatids
-genetically haploid
mitosis
- 2 cells
-both memebers of each pair of chromosomes
-genetically diploid
Rule #1 probability
probability of 2 independent events occuring together is the product of the probability of their individual occurences (RrxRr = 50% of “R” offspring)
Rule #2 probability
Probability of one or the other of 2 mutually exclusive events occurring is = to the sum of the probabilities of their occurrences
geno vs pheno ratios
G= 1:2:1
P= 3:1
Dominance
Interaction between alleles and a single locus, allele with greater effect is dominant
epistasis
interaction among gene at different loci, the allele present at one or more loci
sex-linked
pattern of inheritance for genes located on sex chromosomes
differs from mendelian pattern
-lack corresponding regions of DNA
sex limited inheritance
phenotypic expression is limited to 1 sex
- milk production in female cows
-hormonally conditioned
-most are autosomal
sex-influenced inheritance
modes of gene expression differ between males and females
-allele may be dominant in male and rec. in female
-can show up in both, but one more frequent in one sex
law of segregation
seperation of paired gene during gamete formation=meiosis
- gametes contain half the #of chromosomes and genes than normal body cells (somatic)
law of independent assortment
Independent segregation of genes at different loci
-all combos are possible
-crossing over
-ensures genetic variability
-cant predict what combo of genes will be present= why siblings dont look alike
marker assisted selection
selection for specific alleles using genetic markers
-closely linked to loci of interest
-visual phenotype
gene transfer
transplantation of specific genes from one individual to another using lab techniques
