Genetics Flashcards
1
Q
what are biological characteristics and give examples.
A
heritable traits… height, skin color, eye colour, and developmental and control processes run by enzymes
2
Q
what are acquired characteristics… give 2-3 examples
A
characteristics that cannot be inherited
e.g. learned skill or knowledge and muscular development
3
Q
if the parent is a genius or a bodybuilder, what will the child inherit
A
brain cells but not the knowledge, muscles but not the developped muscles
4
Q
on what organisms did Mendel do most of his work and what did he observe?… What results emerged from his work?
A
on pea plants. He chose seven characteristics that are easy to quantify and qualify. Mathematical analysis that gave the Mendel Laws.
5
Q
Why did Mendel choose garden pea plants to do his work?… include the name of the specie
A
He chose to work on Pisum sativum because hybrids can be produced and have a short generation time. They can also be self-fertilized or fertilized
6
Q
What didn’t Mendel know when elaborating the conclusions of his studies?
A
the existence of meiosis or genes and chromosomes
7
Q
What 2 principles resulted from Mendel’s work
A
Principle of segregation and principle of assortment
8
Q
what are reciprocal crosses
A
If A X B is the initial cross, then B X A is the reciprocall cross
9
Q
what is a monohybrid cross
A
a cross that studies only two variations of a single trait
10
Q
what is the modern explanation of what Mendel observed
A
characteristics are controlled by genes, which are located on the chromosomes. Each chromosome contains a large number of genes.
11
Q
what is a gene and what is it made up of?
A
basic unit of heredity… made up of DNA and a unique group of nucleotides
12
Q
what do genes do
A
they contain information to make proteins (enzymes), which work in an assembly line fashion and produce substances that affect reaction developments
13
Q
what is the gene locus
A
the specific location of a gene on a chromosome (which is a predicatble location)
14
Q
how many copies of a given gene exist for each characteristic
A
two, one on each member of a homologuous pair of chromosomes
15
Q
what is the name of the alternative form of a gene
A
allele. If a gene occurs in two forms, it has two alleles
16
Q
what is the dominant allele
A
the allele that masks the presence of another different allele
17
Q
what is the recessive allele
A
the allele that is masked by a dominant allele
18
Q
what is the genetic notation
A
dominant allele is shown by capital letter and the letter is associated with the trait of the DOMINANT allele. Recessive allele is designated by lower case letter (same letter than the dominant allele).
e.g. a heterozygous tall male would be Tt
19
Q
what is the genotype
A
the short hand notation for the combination of alleles present in an organism
20
Q
what is the phenotype
A
the appearance of the characteristics
21
Q
what is the principle of segregation
A
the fact that two alleles for a gene are segregated during gamete formation and rejoined at random during fertilization (one from each parent)
22
Q
what is the expressed phenotypic ratio when crossing two heterozygous individuals
A
a 3:1 ratio dominant to recessive
23
Q
what is the modern explanation for the principle of segragation
A
with meiosis, there are 4 resultant daughter cells that each have one set of chromosomes (gametes)
24
Q
what is the gamete ratio of a homozygous parent
A
100% of the gametes will carry the same allele
25
what is the gamete ratio of a heterozygous parent
50% will carry one allele and the other 50% will carry the other allele
26
how can we determine if a dominant individual is heterozygous or homozygous... how is this procedure called
by crossing it with a recessive individual and observing the results. If homozygous, there will be no recessive children. This is called a test cross.
27
what does the principle of independent assortment state
that in a dihybrid cross, the segregation of the two allele pairs is independent
28
why is the segragation of the allele pairs for a dihybrid cross independent
because there is an independent alignment of the chromosomes pairs during metaphase 1
29
what is the expected phenotypic ratio when crossing two heterozygous individuals in a dihybrid cross (heterozygous for both traits)
a 9:3:3:1 ratio
30
how many pairs of autosomal chromosomes are there for humans and what type of genes do these carry
there are 22 pairs, which carry genes that are necessary for normal development
31
how many pairs of sex chromosomes do humans have and what do they carry/control
1 pair, which carries the genes that determine the sex and control the development of most of secondary sexual characteristics
32
how many types of sex chromosomes are there in mammals
two types
33
what genes do the X chromosomes carry
the genes responsible for femaleness and other genes that have no counterpart on the Y chromosomes
34
what genes do the Y chromosomes carry
genes responsible for maleness and other genes that have no counterpart on the X chromosomes
35
what is the sex determination pattern for humans, drosophila, birds, grasshoppers/other insects and honeybees
humans/drosophila: XY for males and XX for females
birds: ZZ for the males and ZW for the females
grasshoppers: XO for males and XX for females
honeybes: males are haploid and develop unfertilized eggs (have no father), and females are diploid and develop fertilized eggs
36
in what cells is there X inactivation and what is it
in female somatic cells... one of the two X chromosomes is randomely inactivated during embryonic development
37
what do the inactive X chromosomes condense into
in compact objects called Barr bodies
38
why is X inactivation important
because it ensures an equal level of expression fron the sex chromosomes despite a differing number of chromosomes in males and females
39
what is a sex-linked gene
a gene that is located on either sex chromosome
40
where are most sex-linked genes found in humans
on the X chromosome
41
what is a hemizygous individual
an individual that only has one allele due to the presence of only one sex chromosome
42
give 2 examples of sex-linked genes for humans
red-green colorblindness and hemophilia
43
how can the location of a particular gene be seen
by tagging isolated chromosomes with a fluorescent dye that highlights the gene
44
what does the chromosomal theory of inheritance state (2)
genes have a specific position (loci) on the chromosomes
| it is the chromosomes that undergo segregation and independant assortment
45
from who came the first solid evidence associating a specific gene to a specific chromosome
Thomas Hunt Morgan
46
why did Mendel study fruit flies (4) and what are their complete name
he chose to study Drosophila melanogaster because they are easy to breed in the lab, they breed at a high rate, they have a short lift cycle (2 weeks) and have only 4 chromosomes pairs
47
what are some differences between male and female fruit flies
males are smaller, they have a black cap encircling their abdomen, they have a rounded caudal tip, they have a sex comb and their abdomen has five segments
females are larger, they have stripes that extend across the dorsal abdomen, have a pointed caudal tip, do not have a sex comb and their abdomen has seven segments
48
what are wild type drosophila
the most natural populations of Drosophila. Have a special notation for fruit flies ++
49
what are mutant type drosophila
natural variants. Mutant alleles often designated by abbreviations of the mutant name
50
what is the chi^2 test used for?
to determine if the data corresponds to a given distribution
51
can a hypothesis be proven true? what else can be done
no... instead prove that the alternatives are false
52
what is the null hypothesis and what is its symbol
it is the hypothesis that there is no difference between 2 given data sets (theoretical and experimental). Symbol H_0
53
what conclusion can be reached about the null hypothesis
that we reject it or that we fail to reject it
54
what is the alternate hypothesis (and symbol)?
hypothesis of difference. Generally generated first. CAN NEVER BE ACCEPTED
55
what is the test statistic?
a numerical quantity used in reaching a decision on whether to reject or fail to reject H_0.
56
based on the value obtained for X^2, what conclusion can be reached
if X^2 calc ≥ X^2 crit (theo.), reject H_0
| if X^2 calc < X^2 crit (theo.), fail to reject H_0
57
what conclusion can be reached with the value of p (probability... look in table)
if p ≤ 0.05 reject H_0
| if p > 0.05 fail to reject H_0
58
how is the degree of freedom (d.f.) calculated
d.f.=(#factors (rows)-1)
59
what does each symbol represent in a pedigree
females are circles, males are squares, and matings are lines. Affected individuals are often black.
60
how are individuals and generations labelled in the pedigree
generations are labelled with roman numerals and individuals with arabic numerals
61
what conclusion can be reached if the trait is expressed more frequently in males or females (males for humans)
the trait is sex-linked
62
what conclusion can be reached if the trait is expressed equally for males and females
that the trait is autosomal
63
what conclusion can be reached if all person that have the trait gave a parent that has also the trait
the trait is dominant
64
what conclusion can be reached if some individuals that have the trait have parents that do not possess the trait themselves
the trait is recessive (be careful if it is sex-linked... more complicated)
65
approximately how many genes are there per chromosome
100-1000
66
what are linked genes
genes that are located on the same chromosome but tend to be inherited together
67
how is distance between genes linked to recombination frequency
the farther 2 genes are, higher probability of crossover and higher recombination frequency
68
what are the 6 factors that can cause Mendel's laws to not be observed?
1: polygenic inheritance
2: pleiotropy
3: epistasis
4: degree of dominance
5: multiple alleles for one gene
6: environmental factors
69
what is polygenic inheritance
many traits controlled by the interaction of MULTIPLE GENES and their alleles.
70
how can polygenic inheritance be recognized
continuous nature of the traits, referred to as quantitative traits
71
give 2 examples of polygenic inheritance in humans
human height, skin color
72
what is pleiotropy
single gene can affect more than one trait (single allele has more than one effect on phenotype and can be dominant to one and recessive to other).
73
yellow fur in mice is an example of ____?
pleiotropy
74
what is epistasis
a gene at one locus alters the phenotypic expression of another gene at another locus
75
give 2 epistasis examples
mice: black coat dominant to white but another gene determines if there is pigmentation or not. If the second gene is recessive/albino, the first one will not be noticeable.
corn and the fact that some have a purple pigment.
76
what is degree of dominance and what are the 2 types
neither allele is dominant. 2 types are incomplete dominance and codominance.
77
what incomplete dominance
failure to completely mask the recessive allele. intermediate phenotype like mixture for heterozygotes. e.g. pink flowers
78
what is codominance
for heterozygotes, both alleles can be seen. not a mixture. e.g. roan cattle, blue andalusian fowl, A-type and B-type blood cell coatings.
79
how many alleles can an individual have (no matter of how many exist)
2
80
what is a polymorphic trait
a trait for which MORE than two distinct phenotypes are present in a population due to multiple allelism
81
what is the notation for blood type problems and how to solve them
I^A: type A
I^B: type B
i: type O
both A and B dominant to O but they are codominant to each other
82
what are antigens
substances that stimulate the body to make antibodies. Most are foreign proteins.
83
what are antibodies
substances that react with the antigen that formed them. Most of the time clumping.
84
what is the Rh antigen
another antigen found in red blood cells. People that have it are positive and those that do not are negative.
85
what is erythroblastosis fetalis
the fact that if the dad is RH+ and the mother is RH-, for the first baby, the mom will produce antibodies. With the second babies, the antibodies could destroy the placenta.
86
give an example of environmental factors that break Mendel's laws
in hymalayan rabbits and siamese cats, allele produces enzyme for color only above 30 celsius.
87
what is multiple allele hierarchical dominance
three alleles and phenotypes. if X, Y, Z, then X dominant to Y/Z, Y dominant to Z. Does not occur in nature.
88
what is multiple allele circular dominance
three alleles and phenotypes. if X, Y, Z, then X dominant to Y, Y dominant to Z and Z dominant to X. Does not happen in nature.
89
what are most human genetic disorders commonly caused by
inherited alleles (mostly recessive)
90
what are the two types of alterations of chromosome structure
deletion of parts of DNA
| mutation of DNA
91
what causes disease in terms of genotype and phenotype
the dominant phenotype and the recessive genotype
92
what is Huntington's disease
progressive brain deterioration with effects seen after age of 30. Dominant allele disorder.
93
what is progeria
dominant genetic disorder. Mutation during meiosis. Dwarfism and rapid aging and early death.
94
give 6 examples of diseases caused by dominant alleles
```
Marfan's syndrome (tall/eye effects)
Polydactyly (extra fingers/toes)
Achondroplasia (dwarfism)
Hypercholesterolemia (high cholesterol)
Progeria
Huntington's disease
```
95
what increases the chance of a mating of two carriers of the same rare recessive allele
matings in the same family
96
what is albinism
recessive allele disease. Lack of pigmentation in skin and hair.
97
what is cystic fibrosis
most common lethal genetic disease (recessive). Defective or absent chloride transport channels in plasma membranes causing buildup of chloride outside the cell.
98
what is sickle cell anemia
recessive allele disease. Defect in hemoglobin, the oxygen carrier molecule.
99
what are multifactorial diseases and give examples
diseases that have both genetic and environmental components. e.g. heart disease, diabetes, alcoholism, mental ilnesses and cancer.
100
what is aneuploidy and what is it caused by
condition in which there is an abnormal number of chromosomes. Often caused by nondisjunction.
101
what is nondisjunction and how do the consequences differ for autosomal and sex chromosomes
failure of homologues or sister chromatids to separate properly during meiosis. Severe developmental abnormalities for autosomal chromosomes but not for sex chromosome.
102
what are monosomics
individuals that lose one autosome chromosome (2n-1). Do not survive development.
103
what are trisomics
individuals that have an extra chromosome (2n+1). Usually do not survive development.
104
what are the pairs of chromosomes that allow for the survival of trisomic individuals
13, 15, 18: severe developmental defects. Death within a few months
21, 22: Maturation of skeletal system is delayed and mental development affected. Individuals survive to adulthood
105
what is down syndrome and what is it caused by
trisomy 21. caused by nondisjunction of chromosome 21 during egg formation. Risk increases with age and these children have greater risk of cancer.
106
what is the consequence of nondisjunction of the X chromosomes
one gamete has XX and the other has nothing
107
what happens if an XX gamete combines with a X
XXX individual (triple X syndromome). Zygote develops into a female with 1 functional X and 2 Barr Bodies. Fertility problems but could be fertile
108
what happens if an XX gamete combines with a Y
Klinefelter syndrome. Sterile male with female characteristics and diminished mental capacity. Large hands and feet and long arms and legs
109
what happens if an O gamete combines with a Y
OY individual does not develop and dies. X chromosome needed to survive.
110
what happens if an O gamete combines with an X
Turner's syndrome. Short stature and webbed neck. Sterile females.
111
what happens if there is nondisjunction of the Y chromosome
gametes are YY
112
what happens if an X gamete combines with a YY
Jacob's syndrome. Normal appearance, more testo., taller, persistent acne. Speech and reading problems.
113
what is genetic counselling
process of identifying parents at risk of having children with genetic defects. Assessment of genetic state of early embryos. Predictions
114
give 2 examples of techniques used to diagnose genetic disorders during pregnancy
amniocentesis and chorionic villi sampling
also ultrasound, fetoscopy
115
what is amniocentesis
procedure to diagnose genetic disorders... needle into the uterus to take sample of amniotic fluid. Done during the 4th month. 1 out of 200 can result in fetal death
116
what is chronic villi sampling
removal of cells from the chorion to diagnose genetid disease. Week 8 of pregnancy. Risks of fetal death.
117
how are the results from tests done to diagnose genetic diseases analysed
analysis of the karyotype for chromosomes abnormalities
test for proper functioning of the enzymes
test for specific alleles by sequencing
