Exam 2 Chapter 4, 28, 3, and 6 Flashcards
1
Q
What is epistasis?
A
masking or alternation of the expression of the alleles of one gene by the allelic combos of another gene
2
Q
What occurs to the dihybrid ratio for epistasis?
A
normal dihybrid ratio is modified
3
Q
What is Recessive Epistasis?
A
an individual must be homozygous for either recessive allele to mask a particular phenotype
-ccPP - white
-CCpp - white
- CcPp - purple
4
Q
What is the dihybrid cross-phenotypic ratio for recessive epistasis?
A
9:3:4
5
Q
What is the Gene Modifier Effect?
A
outcome in which the allele of one gene modifies the phenotype of the allele of another gene.
AA/Aa - agouti
aa- black
CC/Cc- color allowed
cc- albino
therefore - there are three possible phenotypes
6
Q
What is dominant epistasis?
A
when the dominant allele of one gene hides the expression of all alleles of another gene.
7
Q
What is the phenotypic dihybrid cross ratio of dominant epistasis?
A
12:3:1
A- white a- color B- yellow b - green
A-B- = white ——> 12/16
A- bb = white
aaB- = yellow ——–> 3/16
aabb = green ———> 1/16
8
Q
What is complementation Epistasis?
A
when two mutant parents are crossed and all F1 are wild type and F2 show both mutant/wildtype phenotypes
9
Q
What is the phenotypic ratio of complementation epistasis?
A
9:7
you need at least one dominant of both genes to get one phenotype. All other kinds of genotypes give one other phenotype.
A- blue a- no color B-red b- no color
A-B- = purple —> 9/16
A-bb = no color}
aaB- = no color}—>7/16
aabb = no color}
10
Q
What is duplicate gene action?
A
Either gene can provide the wild type with a minimum contribution of only 1 dominant allele. Only a double recessive allele contribution from both genes will produce the mutant type
11
Q
What is the phenotypic ratio of duplicate gene action?
A
15:1
12
Q
What is suppression epistasis?
A
One gene fully suppresses the other gene.
13
Q
What is the phenotypic ratio of suppression epistasis?
A
13:3
C- colored c -white
I = inhibition i = no inhibitor
C- I- = white = 13/16
ccI- = white
ccii = white
C-ii = colored 3/16
14
Q
What is sex-limited inheritance?
A
expression of a specific phenotype is limited to only 1 sex
15
Q
Example of sex-limited inheritance
A
Tail/neck plummage in fowl
H - hen feathering
h - cock feathering
female male
HH - hen hen
Hh - hen hen
hh- hen cock
only males experience cock feathering
16
Q
What is sex-influenced inheritance?
A
The expression of a phenotype is influeced by the sex of the individual
17
Q
Example of sex influenced inheritance
A
Pattern baldness in humans
B= bald
B’ = non bald
Female Male
BB bald bald
BB’ nonbald bald
B’B’ nonbald nonbald
The B’ gene is dominant in females and recessive in males
and B is dominant in males and recessive in females
18
Q
Second Example of Sex Influenced Inheritance
A
Length of Index Finger
L = long finger L’ = short finger
L behaves dominantly in females and recessively in males
Heterozygous LL’ in males is short fingered and in females is long fingered.
in males the length of the index fingers is tried to exposure to testosterone in utero, higher test = shorter finger
also a measure of physical aggression only in males.
19
Q
What is quantitative Genetics?
A
study of traits that can me described numerically
20
Q
What are complex traits?
A
traits that are usually controlled by more than one gene and also affected by the environment.
(focus of quantitative genetics)
21
Q
What is a continuous trait?
A
a trait that does not fall into discrete categories
ex. height or weight
22
Q
What are meristic traits?
A
a type of trait that can be described by an integer (whole number only)
bristles on drosophila back
23
Q
What is a discontinuous trait?
A
a trait that can fall into 2 or more distinct categories
white eyed or red eyed fruit flies
24
Q
What statistical model describes quantitative traits?
A
Normal distribution
25
What is continuous variation?
Traits whose phenotypes are controlled by many different genes and environmental factors
aka human weight/skin tone, or fruit size in plants
26
What is polygenic Inheritance?
transmission of traits that are governed by two or more genes
27
What is the quantitative trait locus or QTL?
the location on a chromosome that affects the outcome of a quantitative trait
It identifies on the chromosome the gene/genes that affect the trait by highlight the area on the chromosome that corresponds to the trait
28
Who was the person that accidentally discovered continuous variation by breading a tall x dwarf plant and getting a broad variation in the F2 generation?
Joseph Gottlieb Kolreuter
29
Who was the geneticist that first demonstrated a link from continuous variation to polygenic inheritance by studying wheat in 1909?
Herman Nilsson-Ehle
30
What is implied by the multiple gene/ multiple factor hypothesis?
each gene adds together to create a net sum of the phenotype
In Hermans experiment for example
AABB- red
AABb - dark pink
AAbb - medium Pink
AaBB - dark pink
AaBb - medium pink
Aabb - light pink
aaBB - medium pink
aaBb - light pink
aabb - white
each of these dominant alleles quantitatively adds more redness to the phenotype
31
How to determine the level of environmental effect in quantitative traits?
Categories as seen on normal distributions blur together showing more phenotypic variation
32
How to calculate the ratio of F2 individuals expressing either extreme phenotype?
(1/4)^n
n = # of gene pairs involved
33
How to find the number of distinct F2 phenotypic classes?
2n + 1
n = # of gene pairs involved
34
What are the four main types of RNA?
mRNA, tRNA, rRNA, sRNA
35
What do you call the position of a gene on a chromosome?
locus
36
What do you a call a cell or organism with one complete set of chromosomes?
Haploid
37
What do you call a cell with two complete sets of chromosomes?
Diploid
38
What is a representation of all of the chromosomes of a cell?
Karyotype
39
What are chromosomes that have the same structures and loci called?
Homologous Chromosomes
40
What is a metacentric chromosome?
centromere directly in the middle
41
What is a submetacentric chromosome?
Slightly raised higher than in the middle
42
What is an acrocentric chromosome?
Centromere is very near the top
43
What is a telocentric chromosome?
Centromere is on the top.
44
What are the two purposes of cellular division?
Cell division allows unicellular organisms to create new individuals by asexual reproduction.
This also leads to multicellularity in many organisms.
45
What is binary fission?
The way that procaryotes procreate. They divide into the middle
46
What are the two parts of the cell cycle?
Interphase and mitosis
47
Interphase is divided into 3 main parts, what are they?
G1 = synthesis of of proteins and RNA,
S = synthesis of DNA
G2 = synthesis of proteins and RNA
48
What is the cell not doing during interphase?
Not actively dividing
49
In which interphase state does the most variation with respect to time occur?
G1
Why?
cell can follow 1 or 2:
1. - enter G0 to postpone division or never divide again
--- this is called the restriction point
2. - finish cycle
50
At the end of the S phase the cell has [blank] as many chromatids as it did in G1.
twice
51
How does the definition of chromosome change throughout the cell cycle?
- in G1 (and late M phase) chromosome = 1 chromatid
- in G2 (and early M phase), chromosome = pair of sister chromatids
52
What is the shortage stage of the life/cell cycle?
mitosis
53
What are the two main parts of mitosis?
Karyokinesis : division of the nucleus
and
Cytokinesis: division of the cytoplasm
54
What are the 5 stages of Mitosis?
Prophase, Prometaphase, Metaphase, Anaphase, Telophase
55
What are the characteristics of Interphase (mitosis)?
- has chromatin fibers
- has 2 centrosomes with centriole pairs
- still has nuclear envelope
56
What are the characteristics of Prophase (mitosis)?
- chromosomes condense and pair up into sister chromatids
- Microtubules form the mitotic spindle
- nuclear envelope breaks down
57
What are the three types of microtubules?
1. Aster microtubules
- positioning of the spindle apparatus
2. Polar microtubules
- push the poles away from each other
3. Kinetochore microtubules
- attach to kinetochore and bounds to each centromere
58
What are the characteristics of prometaphase (mitosis)?
- spindle fibers interact with the sister chromosomes
- each kinetochore microtubule is attached to a centromere (captured) or is otherwise depolymerized
59
What are the characteristics of metaphase (mitosis)?
- chromosomes line up in the equatorial plate
- they have reached their maximum contraction
60
What are the characteristics of anaphase (mitosis)?
- centromeres divide in half and the paired sister chromatids separate
- chromatids start to move to their respective poles with the aid of motor proteins
61
What is the difference between Anaphase A and Anaphase B?
A - kinetochore microtubules shorten as they move the chromatids back to their pole
B - Polar Microtubules lengthen as the cell gets larger to keeping pushing the poles away from each other
62
What are the characteristics of Telophase (mitosis)?
- daughter chromosomes reach their respective poles
- chromosomes uncoil and become chromatin
- nuclear membrane reforms into separate nuclei
-Spindle Fibers disappear
63
What is the difference between cytokinesis in an animal vs a plant?
In an animal it forms a cleavage furrow.
In a plant a cell plate is formed.
64
What are coenocytic cells?
A cell when cytokinesis doesn't happen or doesn't happen properly or is absent.
Characterized by being multinucleated
Common in fungi.
65
What does it mean for some eukaryotic species to be isogamous?
this means that they produces gametes that are morphologically similar (identical gametes for both male/female)
66
What does it mean for a eukaryotic cell to be heterogamous?
This means that it produces gametes that are morphologically different like the sperm and egg cells
67
What is the difference between Meiosis I and Meiosis II?
Meiosis I is a reductional division which means that the chromosome # is halved
Meiosis II is a equational division meaning the chromosome # stays the same
68
What are the five stages of Prophase 1?
Leptonema
Zygonema
Pachynema
Diplonema
Diakinesis
69
What happens during Leptonema?
chromatin begins to condense but the sister chromatids are not yet visible
70
What happens during Zygonema?
- Chromosomes further condense
- homologous chromosomes pair up side to side
- male XY chromosomes line up end to end
- each pair of synapsed homologous chromosomes are called bivalents
- synapsis occurs by the synaptonemal complex
71
What happens during Pachynema?
- Chromosomes shorten and thicken to the point where each one is seen as double chromatids
- each bivalent is now a tetrad the sister pair and the non sister pair
- crossing over occurs
72
What occurs during diplonema?
Chromosomes continue to shorten and thicken
- synaptonemal complex breaks down
- homologues start to separate
73
What happens during Diakinesis?
- chromosomes become smallest
- chiasmata begin to move to the end to separate the homologues
-nuclei disappears, spindle fibers start to form
74
What occurs during prometaphase 1?
The spindle apparatus is completed and the kinetochore microtubules attach to the chromatids
75
What happens during metaphase 1?
Tetrads organize along the metaphase plate randomly
A pair of sister chromatids is attached to one pole while the other to the opposite
76
What happens in Anaphase 1?
- the sister chromatids get pulled to their own sides and are now called dyads
- the centromeres do not split
77
What happens during telophase 1?
Dyads go to their respective sides
cleavage furrow forms
and cytokinesis happens
78
What is the short time between the two meiotic divisions called?
Interkinesis
there is no DNA synthesis here
79
What happens after interkinesis?
Meiosis 2
The steps for this are almost identical to mitosis.
In anaphase II when the dyads split they split into monads.
Each of the four cells that are now created are different from the rest which is different from mitosis.
80
What does the chromosome theory of inheritance state?
1. Chromosomes contain genetic material
2. chromosomes are replicated and passed on
3. nuclei of eukaryotic cells contain homologous chromosomes
4. when gametes are formed nonhomologous chromosomes segregate independently
5. each parent contributes one set of chromosomes to off springs
81
Which two people independently came up with the chromosomes theory of inheritance and in which year did they do it?
1902-3 by Theodore Boveri and Walter Sutton
82
What is the sex determination system in mammals?
XY - male
XX - female
83
What is the sex determination system in birds, butterflies, moths, and some fish?
ZW - female
ZZ- male
84
What is the sex determination system found in many insects?
XX- females
XO - males
85
What is the sex determination system found in Drosophila?
X chromosome-autosome balance system
86
What is gametogenesis?
production of gametes
87
In early embryonic development a group of cells become the precursor germ cells, what are they called?
primordial germ cells
88
Where does spermatogenesis take place?
seminiferous tubules
89
What is the progression of PGCs to spermatozoa?
PGCs will divide into spermatogonia by mitosis
During puberty spermatogonia differentiate into primary spermatocytes.
Primary spermatocytes undergo meiosis 1 and become secondary spermatocytes
Secondary spermatocytes under go meiosis 2 and become spermatids
Spermatids further differentiate to spermatozoa.
90
What is the difference between the meiosis of spermatids and oocytes?
spermatogenesis is symmetric
91
Do the daughter cells of spermatogenesis completely seperate?
No, attached by cytoplasmic bridges
92
What are the two types of cells that aid spermatogenesis?
Sertoli cells and Leydig cells
Sertoli cells - aka sustentacular "nurse" cells - produce chemicals that help the sperm mature
Leydig Cells - produce testosterone
93
What is the tightest blood tissue barriers in the mammalian body?
Blood Testis Barrier
94
What is the difference between spermatogonium A and Spermatogonium B?
A - keeps doing mitosis
B - ready for meiosis
95
What is the last stage of spermatogenesis called?
Spermiogenesis
Spermatids -> spermatozoa
1. golgi phase - spermatids develop a head made up by the golgi appartus making the acrosome, other side makes a mid piece with the mitochondria
2. cap phase- acrosome spreads over the nucleus
3. Formation of tail - one centrioles becomes long and becomes the tail
4. maturation phase - the excess cytoplasm / residual body of reguad/ is taken up by the sertoli cells
5. spermiation - spermatozoa are released from Sertoli cells into lumen of seminiferous tubule in a process called spermiation
96
How long does it take a spermatogonia to mature?
9 weeks
97
How much sperm does an adult male produce per day?
100 - 400 million
98
What is the process by which females produce eggs?
Oogenesis
99
Where does oogenesis take place?
ovaries
100
Are the meiotic divisions of oogenesis continous?
no.
101
What is the sequence of Oogenesis?
PGC into oogonia. Oogonia differentiate into primary oocytes. Primary oocytes undergo meiosis 1 where they are arrested in prophase 1.
At puberty, primary oocytes finishes meiosis 1 and makes - secondary oocyte and the first polar body. ( this is what is asymmetric)
Secondary oocyte arrests in metaphase 2 where it enters into the fallopian tubes.
If it is not fertilized it will not complete meiosis 2 and degenerates.
If fertilized it will complete meiosis 2 and will create a second polar body as well as a zygote.
102
What happens to the first polar body?
It degenerates but may develop into two second polar bodies
103
When do oogonia begin to develop into primary oocytes?
The third month of gestation
104
Primary oocytes are arrested in prophase 2 by when?
7th month of gestation
105
What is the X chromosome-autosome balance system found in Drosophila?
The ratio of X chromosomes is the primary determinant of sex in Drosophila.
The y chromosome is not involved in determining sex but just for the production of sperm in flies.
Example:
Drosophila melanogaster has 4 pairs of chromosomes 3 pairs of autosomes and 1 pair of sex chromosomes.
The ratio of X chromosomes to the sets of autosomes will determine sex:
X:A ratio = 1 = female
X:A ratio = 0.5 = male
X:A ratio = 0.5 < X:A < 1 = intersex
X:A ratio > 1 = metafemale
X: A ratio < 0.5 = metamale
106
What will the X:A ratio of 1 give?
Female
107
What will the X:A ratio of .5 give?
Male
108
What will the X:A ratio of 0.5
intersex
109
What will the X:A ratio of > 1 give?
metafemale
110
What will the X:A ratio of <0.5 give?
metamale
111
What insect uses the haplo-diploid system?
bees
112
In the haplo-diploid system males are [blank]
haploid, and produced from unfertilized eggs
113
In the haplo-diploid system females are the workers and the queen and they are [blank]
diploid, and produced from fertilized eggs
114
Who ran the white eyed drosophila experiment and what did he find?
Thomas Hunt Morgan, he found proof of the chromosomes theory of inheritance by describing a case of sex linkage
115
What was the white eyed male drosophila experiment?
White eyed Male drosophila flies crossed with true breeding red eye
F1 = all flies red eyed
F2 =2459 red eyed females
1101 red eyed males
0 white eyed females
782 white eyed males
This means that the white eyed gene has to be on the x chromosome because the F1 flies did not have it
116
What are reciprocal crosses?
A reciprocal cross is a breeding experiment where a male expressing a trait of interest is crossed with a female not expressing the trait, and then a female expressing the trait of interest is crossed with a male not expressing the trait to test the role of parental sex on a given inheritance pattern
X - linked do not behave normally in the reciprocal cross.
117
What do you call genes that are found on one of the two types of sex chromosomes but not both?
Sex Linked
118
What is a hemizygous trait?
A trait in where only one of the two X chromosomes is observed because males have a Y instead of a second X
119
What are genes that are only on the Y chromosomes called?
Holandric
120
What are the parts on the X and Y chromosomes that are kind of homologous called?
Psuedoautosomal regions (pars)
an example is the Mic2 gene used in antibody production
121
What is the primary sex ratio?
Proportion of Males to females
males are heavily favored
122
What is the secondary sex ratio?
Proportion of females to males
males are slightly favored over women
123
What is the genetic dosage problem in Mammals?
There are 2 X chromosomes for women while only 1 Y chromosome for men.
124
What is a barr body?
An inactive X chromosome that can be seen during interphase of a female somatic cell
125
What causes the barr body and who hypothesized it?
Mary Lyon proposed that one of the X chromosomes of the two females have are inactivated randomly in each cell
calico cat pattern is an example of this
126
How to find the number of Barr bodies?
of X Chromosomes - 1
127
What are linked genes?
genes that are on the same chromosome
128
What is a linkage group?
a group of genes on the same chromosome
- corresponds to the haploid number of the chromosome
129
When gene A and B are on two different chromosomes, how are the gametes affected?
gametes are produced in equal proportions
130
When gene A and B are on the same chromosome and are very close to each other, how are the gametes affected?
This is called complete linkage and gametes are in equal proportions
131
When genes A and B are on the same chromosome but are kind of far apart, how are the gametes affected?
This is called incomplete linkage, gametes are produced in unequal proportions
132
When genes A and B are on the same chromosome but are very far apart, how are the gametes affected?
This is called complete incomplete linkage and gametes are produced in equal proportions.
133
What did Sutton point out in regards to chromosomes and Mendelian Factors?
That the many different units on a chromosomes did not assort independently but as a group
134
What were the example of non independently assorting plant traits and who were they found by?
Bateson and Punnett found flower color and pollen shape
135
Who discovered the chiasmata in synapsed homologous chromosomes in 1909?
F.A. Janssens
136
Who discovered the first X-linked gene in Drosophila
Thomas H. Morgan in 1911
137
How to calculate recombination frequency?
(# of recombinant offspring/total # of offspring) x 100
138
What does yy ww mean?
linkage arrangement = unknown
139
What does yw/yw mean?
Loci are on the same chromosomes
140
What are y/y and w/w meaning?
They mean that the loci are on different chromosomes
141
How to calculate map distance?
(Number of recombinant offspring/total number of offspring) x 100
the unites are called map units
also refered to as centiMorgans (cM)
Used to tell how far apart to genes are from each other.
