chapter 13 - patterns of inheritance Flashcards
chromosomes def
long molecules of DNA wrapped around nucleosomes…
what percentage of DNA codes for function protein in eukaryotes… what about prokaryotes?
Around 1% for eukaryotes, 90% for prokaryotes
how many chromosomes do humans have?
46, 23 pairs
how are human chromosomes arranged?
in the order of size, though the last one - #23 is the sex chromosome
human male chromosome
XY
human female chromosome
XX
homozygous def
same alleles
heterozygous def
different alleles
genotype def
the actual alleles inherited
ex: genes coding for flower color AA, Aa, or aa
phenotype def
the physical characteristics or traits of an organism
ex: purple flowers
who and when were the principles of genetics created [by]?
mendel in 1860s
how did mendel create these principles?
used pea-plants which self-pollinate, grow easily + quickly, and have 7 contrasting traits
principle of dominance
1 trait is ALWAYS expressed
principle of segregation
during meiosis homologous chromosomes separate into each cell
what is a cross?
making of 2 organisms
P = ?
parental generation
F1 = ?
first generation
F2 = ?
second generation
how can we predict results?
punnett squares determine probability or chances of a specific outcome
principle of independent assortment
chromosomes segregate independently of one another during meiosis - only get 1 pair of each cell
what other factors can affect offspring separate from predictions?
carrying capacity or amount of resources it can sustain:
I. food
II. water
III. habitat
product rule
chance of 2 or more independent events occurring simultaneously = probability of each multiplied
dihybrid cross def
2 traits, hybrid for both
what kind of a trait is height? what is it influenced by?
Height is a multifactorial trait-
multifactorial inheritance is influence by more than 1 gene and the environment
can some alleles be neither dominant nor recessive?
yes
are traits only controlled by a single allele/gene?
no; many traits are controlling by multiple alleles or multiple genes
what are 4 exceptions to mendel’s law?
I. Incomplete dominance
II. Multiple alleles
III. Codominance
IV. polygenic traits
incomplete dominance def
the heterozygous phenotype is somewhere BETWEEN the two homozygous phenotypes AND NEITHER allele is COMPLETELY dominant OR COMPLETELY recessive
ex: red + white flowers make pink
codominance def
both traits are fully and SEPARATELY expressed
ex 1: red + white flowers make red and white speckled
ex 2: blood type AB - fully A and fully B
what is blood type is an example of?
codominance AND multiple alleles
multiple alleles - genes with more than 2 allele forms : A, B, and i
codominance - blood type fully A and fully B
polygenic inheritance def
a trait produced by two or more genes, and usually shows a RINGE in phenotype
ex: skin color, eye color, height, personality
what can occasionally in polygenic inheritance?
epistasis: one gene overshadows all of the others
ex: labrador retriever fur colors, eye colors, and albinism
[ bad gene(s) make bad traits, all bad people make bad society ]
pleitropy def
genetic effect of 1 gene on multiple phenotype traits- alleles at 1 locus may have effects on 2 or more traits
ex: sickle cell
[ 1 bad gene makes mANY bad traits, bad powerful person make bad… everything]
epistasis def
the interaction between genes at two or more loci…. the phenotype differs from what would be expected if the loci were expressed separately
ex: polygenic
what mendel principle are linked genes an exception to?
principle of independent assortment
linked genes def
genes physically located on the same chromosome will be inherited together
ex: blonde hair + blue eyes, red hair + freckles
how are linked genes separated?
only can be separated by crossing over
the farther the distance between the genes, the greater chance of being unlinked
sex-linked traits def
Y chromosome carry few genes
X chromosome contains MANY genes that affect many traits
ex: colorblindness
sex linked genes def
genes on sex chromosomes
x-linked genes def
genes on the X chromosomes are linked
- females inherit the trait as normal and principle of dominance applies
- males inherit the gene on the X but not the Y
how are x-linked genes passed through parents to children?
moms to sons; dads to daughters
males only have one X, they express it whether it is dominant or recessive
