genetics (81) Flashcards
(123 cards)
1
Q
What is genetics?
A
Scientific study of heredity & variation (of inherited characteristics)
2
Q
Define heredity.
A
Passing of traits (chromosomes) from parents to offspring
3
Q
What is a gene?
A
Pieces/portions of DNA that ‘codes for a particular trait’
4
Q
What is a locus?
A
Specific locations for genes
5
Q
What is chromatin?
A
Tangled strands of DNA & proteins within a eukaryotic nucleus
6
Q
Define chromosome.
A
Thread-like structures in the nucleus
7
Q
What is an unduplicated chromosome?
A
Made up of a single DNA molecule & its associated proteins
8
Q
What is a duplicated chromosome?
A
2 sister chromatids, which are the identical copy of a single chromosome
9
Q
What is mitosis?
A
Eukaryotic cells’ nucleus is divided equally into 2 new nuclei
10
Q
What is cytokinesis?
A
A eukaryotic cell divides its cytoplasm into 2 new daughter cells
11
Q
Define sexual reproduction.
A
Production of offspring through fusion of 2 sex cells; genetically variable
12
Q
What are the advantages of sexual reproduction?
A
- Variable offspring can be better adapted to new environments
- Some will survive
*Genetic diversity
13
Q
What are the disadvantages of sexual reproduction?
A
- Must have specialized organs to produce sex cells
- Requires lots of energy
- Biologically costly
- Animals - vulnerable to predators, Plants - producing flowers requires the production of nectar for pollinators
14
Q
What is asexual reproduction?
A
Production of offspring from a single parent through mitosis & cell division
15
Q
What are the advantages of asexual reproduction?
A
- Direct & invariable heredity
- No need for mate, special organs, or mating behaviors
16
Q
What are the disadvantages of asexual reproduction?
A
- Invariable offspring may not adapt to environmental changes
- May become extinct
17
Q
Give examples of asexual reproduction in plants.
A
- Plants - roots/shoots that develop into new plants (e.g., strawberries, dandelions)
- Budding - New individual develops from outgrowth of body of organism (e.g., hydra, yeast)
- Fragmentation - Parts of fungi break off and grow independently (e.g., mushrooms, starfish)
18
Q
What are the advantages of cloning (asexual reproduction)?
A
- Mass production of prized animals/plants
- GMOs for insulin production
- Saving endangered species
19
Q
What are the disadvantages of cloning (asexual reproduction)?
A
- Unethical
- High cost
- Invariable offspring cannot adapt to changing environments
20
Q
What is a haploid cell?
A
A cell containing half the usual number of chromosomes
Example: Sex (stem) cells
21
Q
What is a diploid cell?
A
A cell containing 2 copies of each chromosome
22
Q
What is meiosis?
A
A 2 stage cell division in which resulting daughter cells have half the number of chromosomes as the parent cell; forms gametes (sex cells)
23
Q
How many daughter cells does meiosis produce?
A
4 non-identical haploid daughter cells (gametes)
24
Q
What occurs during interphase I?
A
Growth & DNA replication
25
What happens during prophase I of meiosis?
Chromosomes shorten & thicken, exchange genetic information, and are now 2 sister chromatids.
These chromosomes come together in homologous pairs, called tetrads, and is a process called synapsis. Crossing over (mixing of non-sister chromatids of a homologous pair) occurs.
26
What is a tetrad?
A pair of homologous chromosomes, each chromosome has 2 sister chromatids, so in total 4 chromatids
27
What is synapsis?
Physical pairing of homologous chromosomes during prophase I of meiosis
28
What occurs during metaphase I?
Tetrads move to the centre of the cell, aligning their centromeres across the middle of the cell.
29
What happens during anaphase I?
Homologous chromosomes move to opposite poles of the cell. Reduction division occurred, where only 1 chromosome from each homologous pair will be found in each new daughter cell.
30
What is telophase I?
Nuclear membranes begin to form around chromosomes at each end of the cell, and the cell divides, becoming 2 haploid cells
31
What is spermatogenesis?
Production of sperm cells
32
What is oogenesis?
Production of egg cells
33
Is there interphase II?
NO
34
What happens during prophase II?
Nuclear membrane dissolves and spindle fibers begin to form.
35
What happens during metaphase II?
Chromosomes arrange across the middle of the cell, each with 2 sister chromatids attached at the centromere.
36
What happens during anaphase II?
Sister chromatids separate and move to opposite poles of the cell.
37
What happens during telophase II?
Nuclear membrane forms around the chromatids, now called chromosomes.
38
Mitosis vs. Meiosis
Mitosis: Single division, identical daughter cells, 46 chromosomes in end, diploid daughter cells, makes new body cells
Meiosis: 2 divisions, non-identical daughter cells, 23 chromosomes in end, haploid daughter cells, makes gamete (sex cells, sperm & egg) cells
39
Homologous chromosomes
similar in shape, size, & genetic information. Humans have 23 homologous chromosomes in our body cells (22 pairs of autosomes & 1 pair of sex chromosomes). They separate during Anaphase I.
40
What is a karyotype?
A karyotype is the complete set of chromosomes in an organism.
41
What is non-disjunction?
The failure of homologous chromosomes to move to opposite poles of the cell during meiosis
## Footnote
This results in an abnormal number of chromosomes in the daughter cells, specifically gametes with 24 or 22 chromosomes in humans.
42
What are the consequences of non-disjunction?
One daughter cell has an extra chromosome while the other is missing a chromosome
## Footnote
These cells cannot function normally.
43
What is trisomy?
3 homologous chromosomes in place of a homologous pair
## Footnote
Occurs when a gamete with 24 chromosomes joins with a normal gamete (23).
44
What is monosomy?
Single chromosome in place of a homologous pair
## Footnote
Happens when a gamete with 22 chromosomes joins with a normal gamete.
45
What is Down syndrome?
An extra chromosome 21
## Footnote
Characteristics include a round, full face; short height; large forehead.
46
What is Turner Syndrome?
Turner syndrome is characterized by one X and no Y sex chromosome.
47
What are the characteristics of Turner syndrome?
Female in appearance, do not mature sexually, most miscarried before 20th week of pregnancy
48
What is Klinefelter syndrome?
2 X and one Y sex chromosome
## Footnote
Males are usually sterile and exhibit some feminine body characteristics.
49
What is prenatal testing?
Testing for a genetic disorder that occurs prior to birth
## Footnote
This includes methods such as amniocentesis.
50
What is amniocentesis?
A procedure using a long syringe and ultrasound to obtain cells from the fluid-filled sac surrounding the fetus
## Footnote
This is done when the fetus is large enough.
51
What are autosomes?
All chromosome pairs except for sex chromosomes
## Footnote
In humans, there are 22 pairs of autosomes.
52
What are sex cells?
Chromosome 23
## Footnote
They determine the sex of the offspring.
53
What are the 2 strands of a double-stranded chromosome called?
sister chromatids
54
Describe what happens during Anaphase I of meiosis.
spindle fibres contract, separating homologous pairs of chromosomes
55
Describe what happens during Metaphase of mitosis.
spindle fibres pull chromosomes into a single line along the equatorial plate
56
Is Metaphase of mitosis more similar to Metaphase 1 or Metaphase 2 of meiosis? Explain.
Metaphase of mitosis is more similar to Metaphase 2 of meiosis. In both, chromosomes line up in a single line along the equatorial plate.
57
What are 2 purposes for cells in an organism to undergo mitosis?
* growth
* repair (replacement of damaged or dead cells)
58
Define and contrast diploid and haploid.
* diploid describes a cell with 2 sets (or the full set) of chromosomes
* haploid describes a cell with 1 set (or half of the full set) of chromosomes
59
What is the only type of cell that could not be used for cloning an individual organism?
a gamete because it doesn't contain the full set of an organism's chromosomes
60
Name the only type of cell that undergoes meiosis in a human male.
spermatocytes (in the testes of the human male)
61
What is synapsis and when does it occur during meiosis?
Synapsis is the pairing of homologous chromosomes. It occurs during Prophase 1 of meiosis.
62
What is crossing over and when does it occur during meiosis?
Crossing over is the exchange of genetic material between 2 homologous chromosomes. It occurs during Prophase 1 of meiosis (and possibly during early Metaphase 1).
63
If an oocyte undergoes meiosis, what does it produce? (Be specific about the number and type of cells it produces)
Meiosis of an oocyte will produce 3 nuclei (polar bodies) and 1 immature egg cell (ootid)
64
A cat has 38 chromosomes in its muscle cells. How many chromosomes does it have in its heart cells?
38 (muscle cells and heart cells are both diploid)
65
What do '2n' and 'n' refer to?
* '2n' refers to the diploid number
* 'n' refers to the haploid number
66
What is a karyotype?
A karyotype is a picture of a cell's chromosomes.
67
How many autosomes are there in a normal human sperm cell?
There are 22 autosomes (and 1 sex chromosome) in a normal human sperm or egg cell.
68
What is nondisjunction?
Nondisjunction is when homologous pairs do not split during Anaphase 1 of meiosis.
69
Name a nondisjunction disorder, and describe its karyotype.
* Down syndrome (trisomy 21)
* Klinefelter's syndrome (trisomy 23, XXY)
* Turner syndrome (monosomy 23, XO)
* Trisomy 13 (trisomy 13)
70
Explain how a trisomic female (XXX) would be produced.
Nondisjunction would have caused the egg cell to have 2 X chromosomes. When it was fertilized by a normal sperm cell, there would be 3 X chromosomes in the zygote.
71
What are 2 events that occur during interphase?
cell growth, repair, normal cell functions, DNA replication
72
What is amniocentesis and what is it used for?
Amniocentesis is the extraction of a sample of the amniotic fluid of an unborn fetus. It can be used to screen for genetic disorders such as Down Syndrome in a fetus.
73
True-breeding
An organism that produces offspring that are genetically identical for 1 or more traits when self-pollinated or when crossed with another true-breeding organism for the same traits.
## Footnote
Example: True-breeding purple flowers that are self-pollinated or crossed with another true-breeding with purple flowers will produce all offspring with purple flowers.
74
P-generation
Parent plants used in a cross
## Footnote
Cross is a breeding of 2 organisms with different traits
75
F1-generation
Offspring of a P-generation cross.
## Footnote
Also called the filial generation. They are monohybrids (differs in 1 characteristic only), so only studies inheritance in 1 trait
76
F2-generation
Offspring of an F1-generation cross
## Footnote
Studies inheritance of both traits.
77
Monohybrid cross
Cross designed to study inheritance of only 1 trait
78
Law of segregation
Scientific law, where:
1. Organisms inherit 2 copies of genes; one from each parent
2. Parent organisms donate only one copy of each gene in their gametes (sex cells) because the genes separate during meiosis
79
Allele
A form of a gene. There are at least 2 alleles for each gene (genes come in pairs on the chromosome), where some are dominant and some are recessive. They're inherited from your parents.
## Footnote
Note: A gene is a piece of DNA that codes for a particular trait.
80
Homozygous
An individual that carries 2 of the same alleles for a characteristic.
## Footnote
Example: Both flower colour alleles coded for purple
81
Heterozygous
An individual that carries 2 different alleles for a gene
## Footnote
Example: One flower colour coded for purple, while the other one coded for white
82
Genotype
Genetic makeup/set of alleles of an individual. All forms of genes, including hidden ones.
83
Phenotype
Traits of an individual (appearance). Only expressed alleles (no hidden ones).
84
Dominant allele
Allele that is always expressed, if present.
85
Recessive allele
Allele expressed only if not in presence of dominant allele
## Footnote
Basically... If the individual is homozygous for the recessive allele
86
Test cross
Cross used to see if an individual exhibiting a dominant trait is homozygous or heterozygous for that trait. Done with unknown genotype and homozygous recessive genotype.
## Footnote
If all offspring show dominant phenotype: Homozyous dominant
Both dominant and recessive phenotypes: Heterozygous
87
Punnett square
Diagram showing all possible combinations for each allele
88
Complete dominance
Only one allele is present, despite the presence of the other allele
89
Incomplete dominance
Where neither allele dominates the other and both have an influence on the individual; results in partial expression of both traits. *Genotype still 1:2:1. Only affects phenotype
## Footnote
Example: Snapdragons. Red snapdragon and white snapdragon makes a pink snapdragon
90
Co-dominance
Both alleles are expressed fully to produce offspring with a third (mixed) phenotype. *Genotype still 1:2:1. Only affects phenotype
## Footnote
Examples: Shorthorn cattle (red bull and white cow makes roan (red-and-white) cow)
91
Multiple alleles
Traits controlled by a single gene with more than 2 alleles.
## Footnote
Example: ABO blood type
92
Pedigree
Chart that traces inheritance of a certain trait among members of a family
93
Autosomal inheritance
Inheritance of alleles located on autosomal (non-sex) chromosomes
94
Sex-linked
Describes an allele that is found on one of the sex chromosomes (x or y) and, when passed on to offspring, is expressed
95
X-linked
Phenotypic expression of an allele that is found on the x chromosome (alleles that cause genetic disorders that are only found on the x-chromosome)
## Footnote
Y-linked is the same definition as x-linked but is for y
96
Dihybrid cross
A cross that involves 2 genes, each consisting of heterozygous alleles
97
Law of independent assortment
If genes are located on separate chromosomes, they will be inherited independently of one another
The F2 generation typically has a phenotype ratio of 9:3:3:1
98
What is another term to describe the genotype of a "purebred" organism?
homozygous
99
What is the term used to describe the genotype of an organism that contains 2 different alleles?
heterozygous
100
What is the term that refers to the observable traits of an organism?
phenotype
101
What is the term that refers to the alleles that an individual carries?
genotype
102
List any 2 of the traits of pea plants that Mendel studied?
Any 2 of: seed shape, seed colour, pod shape, pod colour, flower colour, flower position,
stem length
103
In the following Punnett square, what are the genotype ratios of the F1 generation?
T=tall plant t=short plant
T T
t Tt Tt
t Tt Tt
100% heterozygous (100% Tt)
104
In the following Punnett square, what are the phenotype ratios of the F1 generation?
B=brown eyes b=blue eyes B b
B BB Bb
b Bb bb
75% brown eyes, 25% blue eyes
105
What is the purpose of a test cross?
to determine the genotype of an individual showing the dominant phenotype
(the homozygous dominant genotype or the heterozygous genotype)
106
What does a circle represent in a pedigree chart?
a female
107
If a circle/square is coloured on a pedigree chart, what does that indicate?
It indicates that that individual expresses that trait.
108
If a circle/square is half shaded on a pedigree chart, what does that indicate?
It indicates that the individual is heterozygous for the recessive trait (a carrier)
109
In fruit flies, there are 4 alleles for eye colour, and the dominance hierarchy is:
red > apricot > honey > white. In a female fruit fly, how many possible genotypes
are there for red eye colour?
4 (homozygous, and then heterozygous with each of the other alleles)
110
In certain types of cows, there are 2 alleles for hair colour: red and white. When a cow
has the heterozygous genotype, its phenotype is roan (red hairs and white hairs present).
What is this an example of?
codominance
111
Give an example of codominance in human blood type alleles.
AB blood. A (I A) and B (I B) alleles are codominant
112
When a snapdragon flower is heterozygous and contains both the red allele and the white
allele, its phenotype is a pink flower. This is an example of...
incomplete dominance
113
If genes are on located on separate chromosomes, they are inherited independently of
each other. This is called the law of ...
independent assortment
114
In guinea pigs, black coat colour (B) is dominant over white (b), and short hair lenth (H) is
dominant over long (h). What is the genotype of a guinea pig that is homozygous for black
and heterozygous for short hair?
BBHh
115
If a trait is sex-linked, how many possible genotypes are there for this trait in a male?
2
116
If a trait is sex-linked, how many possible genotypes are there for this trait in a female?
3
117
What blood type is the "universal donor" (i.e. it will be accepted by people of any blood
type)?
Which is the "universal acceptor" (can accept any type of blood)?
1. type O (more specifically type O negative) [O negative blood donors are universal because there's nothing in their blood for a patient's antibodies to 'attack'.]
2. type AB (specifically type AB positive) [People with type AB+ blood are universal recipients because they have no antibodies to A, B or Rh in their blood and can receive red blood cells from a donor of any blood type.]
118
Red-green colourblindness is caused by a recessive sex-linked allele. If you have a mother with normal vision and a father who is colourblind, is it possible for them to have a daughter who is colourblind?
only if the mother is heterozygous for (or a carrier of) colourblindness
119
What is point mutation?
A small change in nitrogenous base sequence of a DNA (a single-base pair)
120
Types of point mutations?
1. Base-pair substitution: ACA > AGA
2. Insertion: ACA > ATCA
3. Deletion: ACA > AA
121
What is chromosome mutation?
Error that involves the entire chromosome or a large part of a chromosome (ex. nondisjunction which is the failure of homologous chromosomes or sister chromatids to separate properly during cell division)
122
What is spontaneous mutation?
Occurs randomly, by accident.
## Footnote
Ex. Errors in cell division
123
What is induced mutation?
Occurs because of exposure to outside factors (environmental)
## Footnote
Ex. UV radiation
