Genetics Exam #1

Mechanisms of genetic change/genetic variation

Crossing over occurs in interphase 1 and causes for recombination where homologous chromosomes exchange parts

Mendel's law of segregation

two alleles for each trait separate during gamete formation (meiosis) and then unite at random, one from each parent at fertilization

Mendel's law if independent assortment

alleles of different genes segregate into gametes independently of each other

similarities of Mitosis and meiosis

-all start off as a diploid cell
-goes through interphase first
-both involve cell division
-synthesize DNA first

difference of Mitosis and meiosis

-meiosis divides twice
-meiosis has crossing over
-mitosis preserves genetic material (each daughter cell will get the same amount of DNA)

How to work from Phenotype to genotype

-if the phenotypes has the recessive trait than the organism is homozygous for the trait
-if the phenotypes has the dominant trait presented then need to do a testcross to see if it is heterozygous or homozygous

allele

alternatives forms of a gene

back cross

mixing of a hybrid organism with one of its parents (homozygous parents) and used to isolate a certain gene that scientist want to keep in the line

chromosomes

a structure in the nucleus that contains a linear array of DNA

co-dominance

refers to an a pair of alleles that, bot exert an effect on the phenotype when they are present together

Dihybrid

heterozygous at two different genes

Diploid

having to complete sets of chromosomes, one from mother and one from father

DNA

the molecular of heredity that stores genetic information

gene

a segment of DNA that codes for a protein

Genotype

the specific combination of alleles that an individual possesses at one or more loci

Haploid

having one set of chromosomes

Heredity

Passing of traits from parents to offspring

heterozygous

having two different alleles at a particular locus

homozygous

having two identical alleles at a particular locus

incomplete dominance

form of codominance in which the heterozygote is about half way between the two homozygotes in a phenotypes (pink flowers when the parents are red and white)

Loci

a region of a chromosomes or DNA molecule where a particular kind of gene is located

monohybrid

having two different alleles for a single trait

mutation

heritable alterations in DNA sequence

phenotype

outward appearance of an individual with respect to one or more traits that is associated to with some particular genotype

recessive

refers to an allele that has no effect on the phenotype unless it is present in the homozygous condition

sex cell

a haploid cell that can join with another sex cell to create new life (gamete)

somatic cells

cells that undergo mitiosis

telomere

the ends of the chromosome

test cross

the crossing of an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype

Phenotypic ratio of dihybrid cross

9:3:3:1