Mendelian Inheritance - Week 2 Flashcards
who came up with the pea plant experiment
gregor mendel
what did gregor mendal know nothing about
- dna
- chromosomes
- meiosis
what is the gene
the basic unit of inheritance
what are genes
genes are segments of DNA and genes are short sections of chromosome
How do chromosomes come
as a pair
- one from sire
- one from dam
how many pairs of chromosomes do :
pigs:
humans:
sheep:
cattle/ goats
horse:
dogs/ chickens:
pigs: 19
humans: 23
sheep: 27
cattle/ goats: 30
horse: 32
dogs/ chickens: 39
what is an allele
any one of the alternative forms of a specified gene
e.g black, brown and red hair
define Dominance:
one member of an allelic pair is manifested to the exclusion of the other
define recessive
one member of an allelic pair lacking the ability to manifest itself when the dominant member is present.
what is Mendel’s 2nd law
independent assortment
what happens during gamete formation
segregating pairs of genes assort independently of each other
why do genes on the same chromosome tend to end up in the same gamete
due to crossing over
what does mendels law of segregation state
at species procreation the paired chromosomes split. The chromosomes segregate into the gametes independently of each other
define Genetic Linkage
some alleles on a specific chromosome tend to stay together.
what is crossing over?
exchange of chromosome segments causing genes to recombine
what happens to genes that are closer to the centromere
the less they take part in recombination
what is recombination frequency a measure of
a measure of the linear distance between genes.
-it allows genes to be mapped
what is the unit of a distance
a centimorgan
(recombinant frequency per 1/100 gametes)
what is the ratio of mendelian trait
3:1
Punnett Square
who came up with Dihybrid cross
Gregor mendel
what is a dihybrid cross
cross with two pairs of contrasting traits
example:
- green v yellow
- wrinkled v round
what is Dominance
is the interaction of genes at a locus so that in a heterozygote one allele has more effect than the other
-the allele with the greater effect is dominant over its recessive.
what is complete dominance
the expression of the heterozygote is identical to the expression of the homozygous dominant genotype
what is heterozygote
they have two forms of alleles
e.g Yy
what is partial dominance
the expression of the heterozygote is intermediate to the expression of the homozygous dominant genotype and more closely resembles the homozygous dominant genotype
what is no dominance
the expression of the heterozygote is exactly midway to the expression of the homozygous genotypes
what is over dominance
the expression of the heterozygote is outside the range defined by the homozygous genotypes and most closely resembles the expression of the homozygous dominant genotype.
what gene is horses is partially dominant but cannot be considered good
HYPP
what are the two genes that affect dog coat colour
E gene
- melanocyte stimulating hormone Receptor Gene (MSHr)
B gene
- Tyrosinase Related Protein 1
what does MSHr mean
Melanocyte Stimulating Hormone Receptor Gene
-E gene in dog
what is an epistatic gene
an interaction of genes at different loci such that the expression of genes at one loci depends on alleles present at other loci
what is the “product law “ of probabilities
When two independent events occur simultaneously, their combined probability is equal to the product of their individual probabilities of occurrence.
name the 3 sex related inheritance
- sex linked
- sex limited
- sex influenced
what is sex linked?
pattern of inheritance is located on the sex chromosomes (x & y)
- females carries two X chromosomes
- males have one X (dam) and one Y (sire) chromosome
what is sex limited
phenotypic expression is linked to one sex
- milk yields in cows only
what is sex influenced
modes of gene expression is different between males and females
- dominant in one sex and recessive in another
example of sex influenced inheritance
-Scurs (small, movable horn-like growths)
– Allele for scurs is dominant in males and recessive
in females
– Male only needs one copy to have scurs
– Female requires two copies
what is Mendelian sampling
-The random sampling of parental genes caused by segregation and independent assortment of genes during germ cell formation and by random selection of gametes in the formation of the embryo.
how does mendelian sampling create a problem for animal breeders
- creates problems for Animal breeders as it makes it difficult to predict the outcome of mating
define zygote
a cell formed from the union of male and female gametes.
-has full compliment of genes
