lec 5 patterns of inheritance Flashcards
what are genes?
segment of DNA within a chromosome serving as codes for protein(s)
what is important to note about genes with respect to inheritance?
genes are the basic unit of inheritance
how many chromosomes in a single cell? how many pairs?
46 chromosomes
23 pairs
what are chromomsomes?
long strands of DNA
what is a homologus pair?
pair of chromosomes, 1 from each mother +father
t/f most of our cells contain exactly the same set of genes
true
how many chromosomes do both sperm and egg cells have?
half of a normal cell
23
what are alleles?
alternative versions of a type of gene
explain alleles using the example of a fur color gene in a mouse
-on mouse chromosome is gene for fur color (lets say gene a)
-mice have 2 forms of gene a (1 from mother, 1 from father)
-therefore mouse has two versions of gene a (alleles)
-ex mouse could have 1 black and 1 brown fur allele
individual who carries two copies of same allele is called?
homozygote
heterozygote
individual that carries different alleles
where do alleles originate from?
mutations
what is a mutation?
change in DNA that makes up a gene
t/f all mutations are harmful
false, mutations can be harmful, beneficial or neutral
genotype
genetic makeup of an organism
observeable, physical characteristics of an organism
phenotype
when reading genotypes, what type of letter represents the dominant allele? the ressecive allele?
dominant: capital letters
resscesive: lowercase
what do dominant alleles determine?
phenotype of an organism
what would a genotype look like for a white flower, if the dominant allele is (P) purple and ressecive is (p) white
pp homozygote
-both alleles need to be ressecive for ressecive trait to be phenotype
what is dna’s structure?
double helix
what is the blending theory? note that this theory does not hold up.
offspring should have phenotype that is intermediate between both parents
what is an example of observations not fitting the blending theory ?
eye colour skipping generations in humans
who disproved the blending theory? what was his infamous experiment?
Gregor Mendel
-crossing true-breeding varieties of pea plants
-he found that flower colours were most of the time purple, and occasionally white
what is true breeding?
-parents are self polinated
-offspring are identical to parents
-have the same alleles
what are the 5 points of Mendel’s particulate theory of inheritance
- alleles cause variation in character
- offspring inherit 1 copy of a gene (allele) from each parent
- alleles seperate into different gametes
- gametes can fuse regardless of the allele they carry
- alleles can be dominant or recessive
what is Mendel’s first law of equal seggregation?
states that two copies of each gene (alleles) seperate
what diagram can be used to illustrate Mendel’s first law? why?
punnentt square
-considers all possible combos of gametes
-predicts outcome of cross
what is Mendel’s second law of independant assortment?
-gametes=alleles for one trait combine randomly with alleles for other traits
-gametes form, the two alleles of one gene (ex color) segregate during meiosis independantly of any two alleles of other genes (ex texture)
-which allele a gamete receives for gene A has no bearing on allele it receives for gene B
illustrated when tracking more than 1 characteristic
explain independant assortment using texture and color of pea plants? what would the genotype for a yellow round pea be? wrinkled green?
R=round r=wrinkled
Y= yellow y=green
if pea was yellow and round= RRYY
green and wrinkled= rryy
dihybrid crossing: if a truebreeding yellow, round pea (RRYY) was crossed with a truebreeding green, wrinkled pea, what would be the GAMETES? what would be the F1 gen (result)
RY, Ry, rY, ry
F1= RrYy (round, yellow)
how would we illustrate the crossing of F1 generations?
punnentt square, instead of being 2x2, they will be 4x4 because there are more gametes
what is incomplete dominance?
-one allele unable to express full phenotype in
heterozygous individual
heterozygote phenotype that intermediates b/w those of the two homozygotes
what theory does incomplete dominance resemble? what is an example if incomplete dominance?
blending theory but it is NOT bleding theory
crossing snapdragons
red+ white may sometimes result in pink
t/f most characteristics are controlled by multiple genes
true
what is an example that proves most characteristics are controlled by multiple genes?
skin color, humans have diff amounts of melanin in skin
skin color controlled by three genes (A, B, C) that have equal effects
