genetics Flashcards
what theory did they think before mendels research
blending
purple is from red + blue parents
what type of things did Mendel test on
things that can be studied for their heritable characters and traits
peas
are you happy
very
what is P F1 and F2
P= parental generations
first filial generation (kids that came from p)
F2 is when the f1 gen has kids
what’s a monohybrid cross
its when you have things interbreed when they have different traits for one character
ex: color, yellow/green
what did Mendel check for in the peas
shape and trait (wrinkled or not)
what is the ratio of the dominant gene in F1
1:1
what is the ratio of the dominant gene in F2
3:1
what is particulate theory
genes are discrete particles inside organism
they are pairs but they separate when they are a gamete
what’s an allele
different forms of the gene ex(sS)
what is true breeding
its parents that will make kids that ll have their phenotype (F1 will have same look as P)
what is true breeding’s individuals alleles
SS or ss
homozygous
2 of the same allele
if a thing is heterozygous (Ss) can it be true breeding
no
what is phenotype
trait that we can see (texture, color, shape,…)
what is genotype
the composition of the alleles (SS, sS, ss)
what is the law of segreagation
law #1 from mendel
the alleles separate when making gamete
where and what is a gene
a small part of the dna thats at a specific locus (spot)
It codes for a specific function
what does a test cross show you
how do u do it
the genotype of a thing that has dominant phenotype
you make it have kids with one that has the recessive phenotype (has ss genotype)
what will a test cross show if it is heterozygous
1/2 kids will have dominant and 1/2 will have recessive
what does a test cross show if its homozygous dominant
all the kids are dominant trait
what is the law of independent assortment
medels 2nd law
alleles of different genes go into the gametes independently of each other
but some genes on that are on the same chromosome are linked so they move together but the chromosomes segregate independently
what’s a dihybrid cross
its a hybrid cross but with more than one gene (SsYs or )
the gametes will be SY or Sy… on punnet square
what’s the probability of getting SSYy
SS = 1/4
Yy=1//2
1/4*1/2=1/8
what’s a pedigree and why is it used
its to study the phenotype segregation along many generations of related ppl
bc we cant do planned crosses
do human pedigrees show good proportions
no we dont make enough kids
can you have something neither of ur parents have if its an autosomal dominant inheritance being studied
no
if you have kids and you have an affected gene but your partner doesn’t how many kids will be affected
1/2
awhat’s an autosomal dominant inheritance
A Pedigree analysis of the dominant allele for a given phenotype
are guys less likely to have the affected phenotype (ex: freckles, widows peak, dimples)
no both sexes have same chance
what’s autosomal recessive inheritance
its a pedigree analysis of the recessive allele for a phenotype
What does it mean when a kid has phenotype that neither parent has and what type of pedigree analysis tells you this
it means its a recessive trait and the parents are heterozygous
why do different alleles exist
genes are subject to mutation
what is the wild type
its the most common allele in the populatio
Whats the mutant allele
its the less common allele that is different from the wild type
there can be more than one
what is the incomplete dominance mode of inheritance
it is when a heterozygous individual’s f2 generation has different phenotype kids and some of them are blends
ex:pink flowers can have F2 genes with red, pink and white kids
or curly, wavy and straight hair
what does incomplete dominance mode of inheritance disprove
the blending theory
what is codominance
when 2 different alleles of a gene are in the heterozygote
both of them have have an effect on the same trait
ex: pink flower has r and R it makes it a mix or red and white
ex: AB blood, not AA or AO
what’s a pleitropic allele
an allele that causes more than one distinguishable phenotypical effect
they are cuased y the same protien made by the same allele.
ex: crossed eyes in siamese cats and their fur
what is epistasis
its when one allele covers up or modifies the expression of another genes allele
ex: labs have Black and brown but at another locus there E (pigment) and e (no pigment) so if its ee the dog will be yellow no matter the b/B
what are complementary genes
a form of epistasis
two genes that depend on each other
for example, for a flower to be purple it needs to have a dominant phenotype for 2 genes if not for one it won’t be purple
what are the names of the groups of many genes that control complicated characteristics like height and skin color
quantitative trait loci
or
polygenic inheritance
how do quantitative trait loci/polygenic inheritance work
each allele intensifies or diminishes the phenotype.
the variation it makes is continuous/quantitative
what are the two factors that allow for variation
- multiple genes with multiple alleles (polygenes)
- environmental influences on the expression of the gene
what can make some genotypes have a higher frequency
the loci of the gene
if they are absolute/total linkage of locis they won’t be separated when crossing over but this is rareeee for alll of the genes to be close together
what happens when genes are far apart on a chromosome, what if theyre close?
far: more likely to be separated during crossing over
close: less likely to separate during cross over (prophase)
what is recombinant frequency
its the progeny that is present after crossing over
it is repeatable proportions (based on loci of the alleles)
what’s a recombinant
a genotype different from parents thats caused by cross over
what are genetic maps
they show the arrangement of the genes on the chromosome in mu (map unit)
what is a map unit
1 mu= 0.01 recombination frequency
also known as centimorgan (cM) = mu
how is sex determined for humans and grasshoppers
humans: xx=girl xy=guy grasshopper: XX=girl X=guy both are determined by sperm and its 50/50
turners syndrome
xo (missing an x/y)
it makes a female that is physically abnormal but mentally fine
what is Klinefelter syndrome
XXY
makes a guy that is talll and sterile
what is the SRY
sex determining region on the Y chromosome it makes the DAX1 (anti testis on X chromosome) not work
what happens if youre XY but missing the SRY on the Y chromosome
your phenotypical a girl
what happens if you are XX but have a small piece of Y (the SRY)
you a Guy
what’s an x linked recessive
- its a phenotype that appears more for guys
- if a male with the mutation has kids only his daughters can get it (and if they get it and have one mutant X they are heterozygous carrier’s)
what’s x linked dominant phenotype
- never passed from dad to son
- all girls of accepted dad and normal mom have it but all sons are normal
- if mom is affected but not dad. 1/2 sons are affected and 1/2 daughter’s
y linked phenotypes
passed from father to son
mitochondrial (maternal) inheritance
mitochodria, chloroplast and plastids have a bit of dna
they are passed on by the mother
what does a pedigree analysis of mitochodrial phenotypes show
an affected mom passes it to all her kids
an affected dad doesn’t pass it
