Ch. 17 - simple patterns of inheritance Flashcards
(35 cards)
1
Q
P generation
A
- true breeding parents
2
Q
F1 generation
A
- offspring of P cross
- monohybrids
- all show dominant trait
3
Q
F2 generation
A
- offspring of self-fertilized F1
- recessive trait reappears
- 3:1 ratio for phenotype
- 1:2:1 ratio for genotype
4
Q
main drawback of Mendel’s experiment
A
- took ages cuz he had to wait for the plants to grow and could only grow them in certain seasons
5
Q
Mendel’s three important ideas
A
- traits are dominant and recessive
- genes are the “unit factors” for inheritance and each gene has two variants called alleles
- segregation of alleles - two copies of a gene carried by an F1 plant segregate from each other so that each sperm or egg only has one allele
6
Q
Mendel’s law of segregation
A
- two copies of a gene segregate from each other during the transmission from parent to offspring
- explains his observed ratios
- explained by pairing and segregation of homologous chromosomes during meiosis
7
Q
genotype
A
- the genetic composition of an individual
TT- homozygous dominant
Tt - heterozygous
tt - homozygous recessive
8
Q
phenotype
A
- physical or behavioral characteristics that are the result of gene expression
ex:
TT and Tt are tall
tt is dwarf
9
Q
how do you set up a punnet square
A
- write down genotypes of parents (with male on top and female on the side)
- write down possible gametes that each parent can make
- fill in the possible genotypes for the offspring
- determine relative proportions of genotypes and phenotypes
10
Q
can you predict the phenotypic/genotypic ratios of four individuals?
A
no - because of random sampling, you need a much larger sample size to be able to see the ratios
11
Q
testcross
A
- you can’t know the genotype of a dominant phenotypic individual
- cross with a recessive individual (know there’s two recessive)
- if some of the offspring are dwarf, unknown is Tt
- if all offspring are tall, unknown is TT
12
Q
two- factor cross
A
- follows inheritance of two different traits
- can determine linkage
13
Q
two possible linkage patterns
A
- linked - variants found together in parents are always inherited as a unit
- independent - variants are randomly distributed (9:3:3:1 phenotype ratio)
- Mendel’s discoveries were consistent with independent assortment
14
Q
Mendel’s law of independent assortment
A
- alleles of different genes assort independently of each other during gamete formation
- not always true
15
Q
chromosome theory of inheritance
A
- chromosomes contain the genetic material
- chromosomes are replicated and passed from parent to offspring
- the nucleus of a diploid cell contains two sets of chromosomes (one from mom, one from dad) that are found in homologous pairs
- at meiosis, one member of each chromosome pair segregates into each daughter cell
- gametes are haploid cells that combine to form a diploid cell
16
Q
locus
A
- physical location of a gene of a chromosome
17
Q
how does random alignment affect gene inheritence
A
- during meiosis 1, the chromosomes are assorted independently and randomly, which creates genetic variation in gametes
18
Q
pedigree analysis
A
- analyzes an inherited trait over the course of several generations in one family
- females are circles
- males are squares
19
Q
are genes for diseases more likely to be found on X or Y chromosomes?
A
- X because it’s a bigger chromosome
20
Q
types of disease genes
A
- recessive or dominant
- autosomal or sex-linked
21
Q
examples of dominant and recessive diseases
A
- recessive - cystic fibrosis
- dominant - huntington disease
22
Q
different mechanisms of sex determination in animals
A
- haplo-diploid (bees)
- male is haploid and female is diploid
- X-O (certain insects)
- Z-W (birds)
23
Q
X-linked traits
A
- only found on the X chromosome
- males are homozygous for X-linked traits
- Y chromosome doesn’t have a backup to cover up a recessive allele, so males are affected by just one recessive
24
Q
Morgan’s experiments
A
- showed correlation between a genetic trait and the inheritance of a sex chromosome
- testcrossed mutant male fly with white eyes (red is wild type)
data consistent with the ida that the eye-color alleles in fruit flies are located on the X chromosome
25
simple mendelian inheritance
- recessive allele does not affect phenotype of heterozygote
- just the dominant allele makes enough functional protein to provide a normal phenotype, masking the recessive allele
-
26
incomplete dominance
- heterozygote shows intermediate phenotype
- neither allele is dominant
27
codominance
- phenotype depends on which two alleles are inherited
- ex: ABO blood types in humans
- AB is codominant because both antigens are present on the blood cells
- A and B are dominant to i
28
the norm of reaction
- the phenotype range that individuals with a particular genotype exhibit under differing environmental conditions
29
gene interaction
- a single trait is controlled by two or more genes, each of which has two or more alleles
30
epistasis
- alleles of one gene mask the expression of the alleles of another gene
- usually because two or more different proteins are involved in a single cellular function
ex: the color of sweet peas is coded for by p and c genes - need at least one dominant of both to show purple
31
discrete traits
- clearly defined phenotypic variants
ex: purple vs. white flowers, red vs. white eyes
32
quantitative
- continuous variation over a range of phenotypes
- typically polygenic
- ex: height, skin color, etc.
33
are most traits discrete or quantitative?
quantitative
34
polygenic
- trait coded for by multiple genes
35
random sampling error
- deviation between observed and expected outcome
- larger samples have smaller sampling errors
