Chapter 6 Flashcards
Genetics
the science that describes the inheritance of traits from one generation to another
Gene
a length of DNA coding for a particular gene product, is the fundamental unit of inheritance
Alleles
different versions of a gene
Genotype
is the DNA sequence of the alleles a person carries
Heterozygote
a person carrying two different alleles at a given locus
Homozygote
individual carrying two identical alleles
Phenotype
is the physical expression of the genotype
Incomplete dominance
phenotype of a Heterozygote is a blended mix of both alleles
Codominance
two alleles are both expressed but not blended
Meiosis
reduces the number of copies of each chromosome from two to one
Difference between mitosis and meiosis
replication of the genome is followed by one round of cell division in mitosis and two rounds of cell division in meiosis, meiosis I and meiosis II
In meiosis, recombination occurs between homologous chromosomes
Bivalent or tetrad
Homologous chromosomes that align themselves very precisely with each other in synapsis, with the two copies of each gene on two different chromosomes
Nondisjunction
failure of chromosomes to separate correctly during meiosis
Gametes resulting in nondisjunction
will have two copies of a given chromosome
Law of segregation
states that the two alleles of an individual are separated and passed on to the next generation singly
Law on independent assortment
states that the alleles of one gene will separate into gametes independently of alleles for another gene
Pure-breeding strain
A group of identical individuals that always produce offspring of the same phenotype when intercrossed
Rule of multiplication
the probability of both of the two independent events happening can be found by multiplying the odds of either event alone
A*B = AB
Rule of addition
calculate the chances of either of two events happening. (A+B) - (AB) = A or B
Linkage
failure of genes to display independent assortment
when genes are located close to each other on the same chromosome, they will display linkage and may not assort independently
Recombination
produces new combinations of alleles not found in the parent and also allows genes located on the same chromosome to assort independently
Frequency of recombination between two genes on a chromosome is proportional
to the physical distance between the genes along the linear length of the DNA molecule
The farther two genes are away from each other, the greater the odds that recombination will occur between them
RF= Recombination frequency
(number of recombinants)/(total number of offspring)
Autosomal dominant
in which case a single copy of the allele will confer the trait or disease phenotype
Does not skip generations male and females affected equally, affected parent passes trait to either all or half of the offspring
Autosomal recessive
in which case two copies of the allele are require for the affected phenotype
can skip a generation, number of affected males is usually equal to the number of affected females
Y-linked
Affects males only; females never have the trait, affected father has all affected sons, unaffected father cannot have an affected son
X-Linke recessive
Can skip generations, tend to affect males more than females, unaffected females can have affected sons, affected female has all affected sons, but can have both affected and unaffected daughters
Pedigree
researchers can determine the pattern of inheritance of a gene, whether it is linked to other genes and whether an individual is likely to pass on a trait to their offspring
Population Genetics
describes the inheritance of traits in populations over time
Population
consists of members of a species that mate and reproduce with each other
Gene pool
sum total of all genetic information in a population
Hardy-Weinberg Law
States that the frequencies of alleles in the gene pool of a population will not change over time, provided that
There is no mutation, migration, natural selection, random mailing, and the population its sufficiently large to prevent random drift in allele frequencies
alelle frequency equation
p+q=1
genotype frequency equation
p^+pq+q^=1
Hardy-Weinberg Equillibrium
After one generation allele frequencies no longer change
