Exam 1 Flashcards
1
Q
The two types of experiments Mendel carried out (explain)
A
- Self fertilization: pollen and egg from the same plant, naturally occurs in peas
- Cross fertilization: pollen and egg from two different plants, produces hybrids (offspring)
2
Q
Describe how Mendel carried out crosses
A
- Remove anthers from flower 1
- Transfer pollen from anthers of flower 2 to the stigma of flower 1
- Plant the seeds
3
Q
define
Characters
A
observable characteristics of an organism
eye color
4
Q
define
Trait
A
specific properties of a character
blue eyes
5
Q
What approach did Mendel use and what does it mean?
A
Emperical approach
* no hypothesis
* quantitative analysis of crosses would provide mathematical relationships that govern traits
* used to deduce empirical laws
6
Q
define
Single factor cross
A
crossing two variants of the same characteristic
7
Q
Describe Mendel’s single factor cross process
A
- Cross two true breadding plants (Parental generation)
- The offspring (F1) self fertilize
- The offspring (F2) are analyzed for their traits
Parental: TT x tt
F1: Tt x Tt
F2: TT + 2Tt + tt
8
Q
result and conclusion of Mendel’s single factor cross
A
- F2 generation had a phenotype of 3:1
- he concluded that this mean that a trait must exist in a dominant and recessive form, not a blended form
- genes are inherited as discrete units
- Law of segregation
9
Q
define
Genes
A
inheritable units that reman unchanged
10
Q
define
Alleles
A
different versions of the same gene
11
Q
explain
Law of Segregation
A
- two copies of a gene seperate from each other during meiosis
- each gamate carries a single allele of a given gene
12
Q
Results/Conclusion of Mendel’s 2 factor crosses
A
- Law of independent assortment
- F2 generation had seeds with new combinations that were not present in the parental generation
13
Q
Law of independent assortment
A
two different genes will randomly assort during meiosis
14
Q
Mendel’s 2 factor crosses has a phenotype ratio of
A
9:3:3:1
15
Q
Pedigree basic symbols
A
- circle = female
- square = male
- filled in = affected
16
Q
Cystic fibrosis
basic facts
A
- recessive disorder
- gene encodes a protein CFTR regulating ion transport
- mutant causes altered CFTR
17
Q
random sampling error
define
A
- deviation b/w observated and expected
- large for small samples
18
Q
Product rule
how to and what it gives
A
- gives the probability that two or more independent events will occur
- multiple probabilities of the independent events
19
Q
Two hetrozygotes for a disease want to start a family, what is the chance their first 3 kids will have the disease (recessive)
A
1/4 * 1/4 * 1/4 = 1/64
0.016
1.6%
20
Q
Binomial expansion equation
what it is and what it gives
A
- gives all possibilities for a given set of unordered events
- P = [n! ÷ (x!(n-x)!)] p x qn-x
- P = prob of outcome
- n = total events
- x = events in one category
- p = probability of x
- q = probability of other event
21
Q
Two brown eyes heterozygotes (Bb) have 5 children. What is the probability that 2 of the cuples 5 children will have blue eyes?
A
P = [5! ÷ (2!)(3!)] (1/4)2 (3/4)3
P = 0.26 or 26%
22
Q
Chi squared
explained
A
- shows goodness of fit aka how close the observed is to the hypothesis prediction
- does not prove hypothesis is correct
x2 = SUM OF (O - E)2 ÷ E
23
Q
High chi square vs low
A
- High indicates low probability that deviations in observed are due to random chance (reject hypothesis)
- low indicates deviations due to random chance (do not reject hypothesis)
24
Q
Process of making a karyotype
A
- sample of blood centrifuged after stopping cells in mitosis
- put in hypotonic solution causes blood cells to enlarge
- Put on slide to see karyotype (organized representation of cell)
25
Humans are _ and have _ number of chromosomes
Diploid, 46 total chromosomes (23 pairs)
26
Homologs
| facts
* form a homologous pair (chromosome)
* nearly identical in size
* have same bandng pattern and genes
* **Not necessarily the same alleles**
27
Chromosomal theory of inheritants
| general concepts
DNA in chromosomes and the chromosomes seperate to make gametes so each parent gives one sent of chromosomes to offspring
28
Explain how Meiosis relates to laws of segregation and independent assortment
* Seperation of homologs during Meiosis shows the law segregation because alleles are seperated
* Lining up on homologs in meiosis explains independent assortment because hetrozygotes can seperate their chromosomes in random ways
29
In fruit flies, sex is determined by
ratio of x chromosomes and number of autosomes
* if X/A = 0.5 male
* = 1 female
30
in bees, sex is determined by
number of autosomes
* males are haploid (1 set)
* females are diploid
31
Simple mendelian
| patterns and molecular explanations
* obey mendel's laws
* dominant/recessive
* 50% of protein from dominant allele is enough for dominant trait
32
Incomplete penetrance
| patterns and molecular explanations
* dominant phenotype is not completely expressed
* dominant allele **is present** but protein not showing effects
* could be because of other genes or enviroment
33
Incomplete dominance
| patterns and molecular explanations
* phenotype in hetrozygotes is a mix of the two alleles
* 50% of the protein from each alleles is not enough to make same trait as 100% of that protein
34
Overdominance
| patterns and molecular explanations
* hetrozygotes have a trait that makes reproductive sucess higher than of either homozygote
* cells may have increased resistance, may produce more protein dimers & increase function, proteins may be produced in more conditions
35
Codominance
| patterns and molecular explanations
* hetrozygote has BOTH phenotypes (not a mash/intermediate)
* example is AB blood type
* alleles encode slightly different proteins so function of each exist together
36
x-linked
| patterns and molecular explanations
* genes are linked to x-chromosome
* 50% of the protein in males is enough for dominant trait but not necessarily in females
37
sex-influenced
| patterns and molecular explanations
* effect of sex on phenotype is different for alleles
* recessive in one sex but dominant in others
* sex hormones may regulate expression of genes
38
sex-limited inheritance
| patterns and molecular explanations
* trait occurs in only 1 sex
* sex hormones may regulate expression of genes
39
lethal alleles
| patterns and molecular explanations
* causes death
* lose of function alleles usually
40
Most recessive mutants are loss of function because
* 50% of the functional protein is enough for the phenotype
* hetrozygote may upregulate normal gene to make up for the loss
41
3 explanations for dominant mutants
* **Gain of function** new or abnormal function of protein
* **Dominant negative** protein acts against normal protein
* **Haploinsufficiency** mutant is loss of function but 50% of protein is not enough for phenotype of wild type
42
Expressivity
degree to which trait is expressed
43
Incomplete dominance
| outcome of single factor cross
* **F1**: 50% of protein not enough so **phenotype is inbetween** two alleles
* **F2 has 1:2:1 phenotype** rather than 3:1 since the heterozygotes have different phenotype
44
Overdominance
| outcome of single factor cross
* hetrozygouse advantage
* genotype AND phenotype of F2 is 1:2:1
* more hetrozygous offspring survive
45
Sickle cell anemia
| explained
* Homozygous for normal hemoglobin are just normal, homozygous for mutant have disease
* Hetrozygotes have adavantage because they do not suffer from sickle cell anemia and are more resistant to malaria
46
Blood type
| explained
* 3 alleles for antigens
* *i* recessive to A and B
* A and B are codominant
* A & B = AB blood type
* A*i* = A blood type
* B*i* = B blood type
* *ii* = O blood type
47
X linked traits
| outcome of single factor cross
F1 phenotpe depends on which parent has mutant/recessive allele
* if father has defective allele, no offspring will be affected but all women will be carriers
* if mother has 2 defective alleles (homozygous) then all daughters will be carries and all sons will be affected
48
Y linked traits
| outcome of single factor cross
* transfered only from father to son
49
Sex-influences traits are ...
| chromosome type
autosomal
50
Lethal alleles
| outcome of single factor cross
Hetrozygoous cross between F1 generation has F2 generation of 1:2 genotypes
* Lethal allele causes death of homozygous alleles for mutant so ratio is not mendelian
51
conditional lethan alleles...
only kill when certain enviromental conditions occur
52
pleiotropy
| definition and causes
multiple effects of a single gene on the phenotype
* gene product can affect cells in multiple ways
* expressed in different cell types
* expressed at different times
53
White spotting phenotype occurs because
alleles that cause decrease in number of precursor cells during development as cells migrate
54
Gene interactions
| definition
occur when two or more different genes influence the outcome of a single trait
55
Epistasis
| definition
the alleles of one gene mask the phenotypic effect of the alleles of a different gene
56
Complementation
| definition
two parents that express same or similar recessive phenotypes produce offspring with the wild type phenotype
57
Gene modifier effect
| definition
allele of one gene modifies the phenotype of the alleles on a different gene
58
Gene redundancy
| definition
a pattern in which the loss of function of one gene has no effect but loss of two has an effect, the genes are reduntant and only 1 is required
59
Epistatic interactions often arise
because 2 or more different proteins may have a common cellular function
60
Epistatis
| F2 generation
F2 would have a different ratio due to masking
* like if gene C and P are both responsible for color
* a dominant C and P allele are both required for purple
* so having a cc or pp allele masks the other gene, even if the other gene has a dominant allele
* CcPp, CCPp, CcPP, CCPP = purple
* ccpp, ccPp, ccPP, Ccpp,CCpp = white
61
Gene redundant
| F2 outcome
15:1 ratio
* Only double recessive genotype has a different phenotype
62
True-breeding tall plants with purple flowers are crossed to true-breeding dwarf plants with white flowers. The F1 plants were tall with purple flowers. The genes that affect these traits independently assort. If the F1 plants were crossed to dwarf plants with white flowers, the expected ratio of the F2 generation would be
1 tall/white flowers : 1 tall/purple flowers : 1 dwarf/white flowers : 1 dwarf/ purple flowers
63
A fruit fly with a diploid set of autosomes has one X chromosome but no Y chromosome. This fly would be _ because _.
male, the ratio of X chromosomes to autosomes is 0.5
64
Two different strains of plant exhibit a recessive phenotype of white flowers. When crossed, they produce offspring with wild-type purple flowers. The outcome of this cross is called _ and it indicates that _
complementation/the recessive alleles are in two different genes
65
Mendelian inheritance pattern rules
| 4 rules
1. Expression of the genes influences traits
2. Genes are passed down unaltered
3. Law of segregation
4. Law of Independent assortment
66
Maternal effect definition
genotype of the mother effects the phenotype of the offspring
67
Maternal effect for shell orientation cross:
Mother *DD* **x** Father *dd*
F1 Genotype: Dd
F1 phenotype: All dextral
68
Maternal effect shell orientation hetrozygous (F1) cross:
*Dd* **x** *Dd*
**Genotype** F2: 1 *DD*, 2 *Dd*, 1 *dd*
**Phenotype**: all dextral
69
Molecular mechanism of Maternal effect inheritance
* **nurse cells** are diploid while oocyte becomes haploid
* nurse cells give their mRNA/protein right after fertilization
* sperm allele too late to express and change development
* these genes play important role in early embryogenesis
70
Epigenetic inheritance definition
* modification alters gene expression
* not permanently changed over generations
* reversible and no change in DNA
71
Dosage compensation purpose and definition
changing gene expression to compensate for differences in sex chromosomes
72
Dosage compensation in mammals general
* inactive x chromosome is condensed down into a **barr body**
* happens during early development
* X chromosome inactivation passed down to *somatic* cells
73
X chromosome inactivation in mammals mechanism
1. **Nucleation**: the number of X-inactivation centers (Xics) counted and chosen
2. **Spreading**: inactivation starts and Xic and progresses until barr body
3. **Maintenance**: barr body stays bar body
74
# define/explain
Pseudoautosomal genes
* genes that are on barr body X chromosome but are expressed
* may involve loosening of chromatin
75
Genomic imprinting
| definition
a segment of DNA is marked to express either maternal or paternal ingerited allele
76
Stages of imprinting
1. Establishment of the imprint
2. Maintenance of the imprint
3. Erasure and reestablishment: *the germ line cell (reproductive) is erased of imprinting to reestablish imprinting based on sex of species (will they pass on silenced alleles or not)*
77
Molecular mechanism of imprinting
* imprinting control region (ICR) near gene
* methylation in genes silences them
78
Maternal inheritance
Genes that are encoded by mitochondrial DNA so only mother passes them down
79
How does variegated phonotype occur in leaves?
* Color of the leaves in in the chloroplast which are maternal inherited
* speices can have cells with different type chlorplasts so they have different colors
80
How does variegated phonotype occur in leaves?
* Color of the leaves in in the chloroplast which are maternal inherited
* species can have cells with different type chloroplasts so they have different colors
81
endosymbiosis theory
chloroplasts and mitochondria were primordial eukaryotic organisms that got endocytosis by an archaea
82
When two different genes are close together on the same chromosome and tend to be transmitted together from parent to offspring, this phenomenon is called
linkage
83
Crossing over occurs during
meiosis
84
_ is needed to produce recombinant offspring.
Crossing over
85
Two genes in Drosophila are found on the X chromosome. A true-breeding fly with white eyes and a gray body was crossed to a true-breeding fly with red eyes and a yellow body. All F1 offspring had red eyes and gray bodies. The F1 female offspring were crossed to male flies with white eyes and yellow bodies. Which F2 offspring is/are recombinant?
Those having white eyes with yellow bodies and red eyes with gray bodies
86
Let's suppose that two genes are linked to each other along the same chromosome and they are 14 map units apart. A true-breeding AAbb individual is crossed to a true-breeding aaBB individual. The F1 offspring are mated to aabb individuals. If this testcross produces 1000 offspring, how many of them would you expect to be aabb?
70
87
In Chi square what hypothesis used and why?
An independent assortment hypothesis is proposed because it allows you to calculate expected numbers of offspring.
88
How to calculate % of recombinant offspring from map distance
map distance = % of recombinant offspring
89
A maternal effect gene exists in a dominant, normal head (N) allele and a recessive, small head (n) allele. A mother with a normal head has a bunch of offspring with small heads. What are the possible genotypes of the mother, maternal grandmother, and offspring
* Mother: nn;
* Maternal grandmother: Nn
* Offspring: Nn or nn
90
With regard to a maternal effect gene, a mother is DD and her haploid oocyte (D is fertilized by a sperm carrying the d allele. Which gene products would be found in this fertilized oocyte?
Only *D* gene products
91
Genomic imprinting is a type of _
epigenetic inheritance
92
The Igf2 gene that is inherited from the mother is silenced due to imprinting. A mutation, which we will call Igf2—, is a loss-of-function mutation. If an Igf2—Igf2 mother is crossed to a father that is Igf2—Igf2, what is the predicted outcome?
Half of the offspring would be normal, and half would be dwarf.
93
Due to imprinting, the gene(s) affecting Prader-Willi syndrome is silenced during egg formation, and the gene affecting Angelman syndrome is silenced during sperm formation. A person named Lynn has Prader-Willi Syndrome due to a deletion that encompasses genes involved with both Prader-Willi syndrome and Angelman syndrome. As an adult, Lynn has child with Angelman syndrome. Lynn is a ______ and the child is _______.
female, male or female
94
What inheritance pattern causes a variegated coat color, such as the Calico cat
X-chromosome inactivation
95
Let's suppose a trait in dogs involves a gene that affects the shape of the spine. This gene exists as the wild-type allele that causes a normal spine and mutant allele that causes a crooked spine. A true-breeding female with a normal spine is crossed to a true-breeding male with a crooked spine. All of the F1 offspring have normal spines. The F1 female offspring are then crossed to true-breeding males with a crooked spine. All of the F2 offspring have normal spines. These are observations are consistent with
maternal inheritance and maternal effect
96
recombinant offspring definition
offspring that have been produced from a crossover event in at least one of the parent's gametes
97
Genes that are _ have a higher probability of crossing over
far apart
98
if there are a small number of recombinant offspring with two genes, those two genes are (far or close)
close to each other
99
chi square formula
x2 = ((observed - expected)2) / expected
100
If reject hypothesis that genes independently assort,
then accept hypothesis that genes are linked
101
genetic mapping purpose
to determine the linear order of linked genes along a chromosome
102
Genes that are far apart result in...
many recombinant offspring
103
map distance equation
mu = (# recombinants / total offspring) * 100
104
test cross definition
individual that is a double (or triple) heterozygote crossed to a homozygous recessive individual
105
multiple cross overs set a quantitative limit on
measurable recombination frequencies as physical distance increases
106
accuracy of recombination frequency calculations from test crosses & map distance
as the map distance approaches 50mu, the number of recombinant offspring is underestimated as a test cross is only expected to yield a max of 50% recombinant offspring always
107
the probability of a double cross over is predicted by...
the product rule
108
product rule equation for probability of double cross over
= (probability of single cross over between genes 1 and 2) * (probability of a single cross over between genes 2 and 3)
109
positive interference
the first crossover between genes decreases the probability that another crossover will occur nearby
110
karyotype features
* location of the centromere
* size
* banding patterns
111
how does staining show banding patterns?
dark bands bind dye very heavily while light bands do not
112
banding pattern is useful because...
* distinguishes individual chromosomes
* detects changes in chromosome structure
* shows evolutionary relationships
113
4 types of centromere locations
* **metacentric**: in the middle
* **submetacentric**: slightly off center
* **acrocentric**: close to the end of chromosome
* **telocentric**: at the end of chromosome
114
G banding numbering convention
each side of the chromosome (p & q) is split into sections (with 1 being the sections closer to the centromere) and each section is divided into bands that are labelled in the same way
**ex.**
*p-2-3*
on the p side of the chromosome (above), section 2 third band
115
4 types of changes that can occur in chromosome structure
* deletions
* duplications
* inversions
* translocations
116
_ and _ change the total amount of genetic material in a chromosome
deletions and duplications
117
_ and _ do NOT change the total amount of genetic material in a chromosome
inversions and translocations
118
inversion definition
change in direction of a section of the chromosome
119
translocation 2 types and definitions
* **simple**: a piece of chromosome gets attached to another chromosome
* **reciprocal**: two different chromosomes exchange pieces that make two abnormal chromosomes
120
nonallelic homologous recombination
**repetitive sequences** cause a misalignment of homologous chromosomes which results in a misaligned cross over. results in duplication or deletion
121
a chromosomal deletion occurs when...
* a chromosome breaks and a piece is lost
122
terminal deletion definition
chromosome is broken into two pieces and the part without the centromere is lost
123
interstitial deletion
chromosome breaks in two places and the two outer pieces reattach and the central fragment is lost
124
duplication usually caused by...
abnormal events during recombination/crossing over
125
gene family definition
two or more genes in a single species that are derived from the same ancestral gene
126
how are gene families formed?
an abnormal event causes a gene duplication, and over generations there are mutations so the two duplicated genes become slightly different
127
paralogs
homologous genes within a species, carry out different but similar functions
128
copy number variation
a segment of DNA that varies in copy number among individuals
129
copy number variation can be caused by
* nonallelic homologous recombination
* proliferation of transposable elements
* errors in DNA replication
130
segmental duplication
one segment of DNA has multiple copies of the same gene
131
comparative genomic hybridization can be used to
detect deletions and duplications
132
how to interpret data from genomic hybridization
* look at the ratio of green to red fluorescence in the hybrid chromosome
* a ratio of 2 indicates a duplication in "green" (cancer cells usually)
* ratio of 0.5 indicates a deletion in green
133
Pericentric inversion
inversion that includes centromere
134
paracentric inversion
inversion not with centromere
135
two ways inversions can alter the phenotype of an individual (very rare)
* **breakpoint effect**: an inversion breakpoint is in the middle of a vital gene
* **position effects**: a gene is repositioned in a way that alters its gene expression
136
crossover betwee a pericentric inverted chromosome and a normal chromosome
results in 2 normal chromatin and 2 chromatin with a deletion and a duplication in each
137
crossover between a paracentric inverted chromosome and a normal chromosome
results in an acentric fragment and a dicentric chromosome
138
reciprocal translocations arise from (and examples)
* chromosome breakage and DNA repair (*ex. reactive ends broken by external factors but DNA repair improperly attaches them back*)
* abnormal crossovers (*nonhomologous chromosomes do crossing over*)
139
_ translocations are more lethal/problematic than _ translocations
unbalanced than balanced
140
in familial down syndrome
* the majority of chromosome 14 gets attached to chromosome 21
* offspring could have 3 copies of genes on chromosome 21 so exhibit similar characteristics of down syndrome
141
balanced carriers of familial down syndrome often have
reduced fertility
142
Robertsonian translocations
* breakage near centromeres of acrocentric chromosomes causes loss of small fragments and fusion of large segments into one chromosome
* most common rearrangement in humans
143
individuals with balanced translocations...
have a larger chance of producing gametes with an unbalanced combination of chromosomes
144
mechanism of gamete formation in individuals with balanced translocations
translocation cross forms where homologous line-up and form a octet
* **alternate segregation**: 2 normal gametes, 2 balanced gametes
* **adjacent-1 segregation**: 4 unbalanced gametes
* **adjacent-2 segregation**: 4 unbalanced gametes *rare one*
145
type of segregation where one cell gets both normal chromosomes and another cell gets both translocated chromosomes after meiosis 1
alternate segregation
146
type of segregation where all four cells have one normal and one translocated chromosome
adjacent-1 segregation
147
semisterility
having fewer variable gametes so individuals fertility is lower
148
euploidy
* variation in the number of complete sets of chromosomes
* organisms with 3 or more sets of chromosomes are also called polyploid
149
aneuploidy
* variation in the number of particular chromosomes within in a set
* organism can be trisomic for that chromosome or monosomic
150
aneuploidy causes an _ phenotype
abnormal
151
why does aneuploidy have a bad effect on phenotype
* genes on that chromosome are expressed 1.5x more
* for trisomy 21 (sex gene) pseudoautosomal genes are expressed imbalanced
152
down syndrome is caused by
* failure of chromosome 21 to segregate properly in meiosis 1
* 5% of the time it is paternal nondisjunction (X and Y not separated in sperm)
153
polyploidy in animals is
lethal usually
154
endopolyploidy
when certain tissues or cells are polyploid in an organism
* enhances the ability of a cell to produce specific proteins
155
polytene chromosomes
a bundle of chromosomes together, aggregate in the chromocenter
156
polyploids with an odd number
are usually sterile as they produce highly aneuploid gametes (chromosome sets don't segregate equally)
157
lgf2 gene is silenced in
sperm
158
leber hereditary optic neuropathy is passed down in what pattern
maternal inheritence
gene in mitochondrial DNA
