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Ch 17 Flashcards

1
Q

Chromosome count in human somatic cells

A

Each somatic cell of a human contains 46 chromosomes.

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2
Q

Homologous chromosomes

A

Chromosome pairs, one from each parent, that are similar in length, gene position, and centromere location.

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3
Q

When in the cell cycle does DNA replication occur?

A

DNA is replicated during the S phase of interphase of the Cell Cycle.

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4
Q

Somatic cell

A

Any cell of a living organism other than the reproductive cells. These cells are diploid.

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5
Q

meiosis in males

A

Occurs in testes; Results in 4 functional sperm cells.

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6
Q

Anaphase I in Meiosis I

A

Homologous chromosomes are separated, leading to a reduction in chromosome number.

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7
Q

What forms when each chromosome pairs up with its homologous chromosome in Prophase I?

A

A Tetrad (4 chromatids total)

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8
Q

Chromosome reduction in meiosis

A

The cells go from diploid to haploid in meiosis I

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9
Q

4 Sources of Genetic Variation

A

1) Independent assortment
2) crossing over
3) random fertilization of gametes
4) mutations

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10
Q

Meiosis takes place in 2 stages.

A

Meiosis I and Meiosis II.

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11
Q

Mutation

A

Mutations are changes in DNA that can occur during DNA replication. They are not specific to sexual reproduction and can be silent, harmful, or beneficial.

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12
Q

Sex chromosomes

A

Chromosomes that determine the sex of an individual.

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13
Q

Meiosis 1 makes ___ cells (how many?) which are ____ (haploid or diploid?), and Meiosis 2 makes ___ cells (how many?) which are ____ (haploid or diploid?).

A

Meiosis 1 makes 2 cells which are haploid, and Meiosis 2 makes 4 cells which are haploid.

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14
Q

In sexual reproduction, how do offspring receive their chromosomes from their parents?

A

Offspring receive half of their chromosomes from the female parent and half from the male parent.

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15
Q

Examples of asexual reproduction in animals

A

Budding: Cells split off the parent organism. Fragmentation: New organisms grow from a separated fragment of the parent organism.

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16
Q

Crossing Over (chiasmata)

A

Exchange of genetic material between homologues, producing chromosomes with genes from both parents. Occurs in prophase I of meiosis I.

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17
Q

Human Somatic Cell

A

Cells have the full number of chromosomes and are diploid (2n).

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18
Q

What happens to genetic material at chiasmata?

A

It can cross over (change places)

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19
Q

What can nonsister chromatids of each homologous pair do during Prophase I?

A

Synapse and form chiasmata

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20
Q

Gamete

A

A mature haploid male or female sex cell.

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21
Q

2^{n}in Independent Assortment

A

2^{n} represents the number of different combinations of chromosomes (maternal or paternal) possible for the gametes due to independent assortment.

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22
Q

Tetrad

A

A group of four chromatids formed by synapsis at the beginning of meiosis (prophase 1).

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23
Q

Asexual reproduction

A

Asexual reproduction results in offspring with chromosomes identical to the parents.

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24
Q

What is the result of crossing over at chiasmata?

A

The resulting chromatid is a recombinant and is genetically different

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25
Meiosis II involves a second division of the two cells produced in Meiosis I.
The result of Meiosis II is four haploid daughter cells.
26
Haploid
A cell or organism having a single set of chromosomes., (gametes)
27
Calculate how many possible unique gametes could form due to independent assortment in an organism with a diploid number of 10.
2^n = 2^5 = 32
28
Chromosomes occur in "matching pairs."
One chromosome of each pair comes from the egg, and one comes from the sperm. The pairs are called homologous pairs.
29
Prophase I in Meiosis I
Homologous chromosomes pair up and form tetrads leading to crossing over of homologous genes between non-sister chromatids.
30
Variations in asexually reproducing organisms?
No differences or variations occur in the offspring; only changes are due to random mutation.
31
Variation in species
The image shows examples of variation in species, such as different patterns in ladybugs and beak shapes in birds. Variations help populations survive environmental change and leads to long-term survival of species.
32
Chiasmata
The point where paired chromosomes remain in contact during prophase 1. Crossing over occurs at chiasmata.
33
Diagram showing DNA replication and homologous chromosomes with specific gene instructions.
DNA replication makes an exact copy of the chromosome. Homologous chromosomes have instructions for the same genes at a specific loci (location).
34
Random fusion of gametes during fertilization
The process where it is random which egg is fertilized by which sperm.
35
Telophase I followed by cytokinesis I in Meiosis I
Leads to the division of cytoplasm into 2 haploid daughter cells.
36
Anaphase II of Meiosis II
In Anaphase II, each chromosome splits at the centromere, resulting in two chromosomes. This process leads to the separation of sister chromatids.
37
Independent Assortment
Random distribution of maternal and paternal homologues to the gametes. Occurs in metaphase 1 of meiosis.
38
Where does meiosis occur?
Meiosis occurs only in reproductive tissues. In males, it occurs in the testes; in females, it occurs in the ovaries.
39
Number of homologous pairs in humans.
Humans have 23 pairs of homologous chromosomes.
40
A cell with a diploid number of 10 will have __ chromosomes per cell after meiosis 1 and __ chromosomes per cell after meiosis 2.
A cell with a diploid number of 10 will have 5 chromosomes per cell after meiosis 1 and 5 chromosomes per cell after meiosis 2.
41
Nondisjunction
The failure of homologous chromosomes or sister chromatids to separate properly during cell division.
42
Calculate how many possible unique gametes could form due to independent assortment in an organism with a diploid number of 16.
2^n = 2^8 = 256
43
Examples of asexual reproduction in plants
Small pieces can be induced to grow independently, such as in strawberry plants.
44
What can nonsister chromatids of each homologous pair do during Prophase I?
Synapse and form chiasmata
45
Telophase II followed by cytokinesis II in Meiosis II
Leads to the division of cytoplasm into 4 haploid daughter cells (gametes).
46
Autosomes
Any chromosome that is not a sex chromosome.
47
Locus
The specific location of a gene on a chromosome.
48
Karyotype
Description gained from analyzing a karyogram including number and visual appearance of the chromosomes in the cell nuclei.
49
Chromosome reduction in meiosis
The cells go from diploid to haploid in meiosis I
50
Is there another round of interphase between meiosis 1 and 2?
No. DNA replication does not occur before the second round of cell division.
51
Meiosis
Meiosis is a type of cell division where daughter cells receive half of the chromosomes of the parent cell. This results in the formation of gametes.
52
In sexual reproduction, how do offspring receive their chromosomes from their parents?
Offspring receive half of their chromosomes from the female parent and half from the male parent.
53
Sexual reproduction leads to variation.
This ensures the survival of a species in difficult times and allows for adaptation to a changing environment.
54
Diploid
A cell or organism having two sets of chromosomes (somatic cells).
55
Human Gamete (sex cell)
Cells have half the number of chromosomes and are haploid (n).
56
Chromosome count in human somatic cells
Each somatic cell of a human contains 46 chromosomes.
57
Example of homologous pairs in how they are similar, and how they may also be different.
Both chromosomes contain instructions for flower color, but one may say "purple color" and the other "white color."
58
Random arrangement of tetrads in metaphase 1
The random arrangement for each tetrad is called the Law of Independent Assortment.
59
meiosis in females
Occurs in ovaries; Results in 1 functional egg (ovum) and 3 nonfunctional polar bodies.
60
Meiosis I is preceded by which phase where DNA is copied?
Interphase
61
Asexual reproduction can lead to difficulty adapting to environmental changes.
Organisms are adapted to the current environment, which may make it difficult to adapt to a changing environment, since they are genetically identical.
62
Zygote
A fertilized egg cell.
63
Metaphase I in Meiosis I
Tetrads (bivalents) line up in the center of the cell.
64
Discuss the affect on the amino acid sequence of the different types of DNA mutations: silent mutation, nonsense mutation, missense mutation, and frameshift mutation.
-silent mutation, no change in amino acid sequence -nonsense mutation, stop codon reached early, protein released incomplete, -missense mutation, incorrect amino acid brought -frameshift mutation, shifts entire reading frame so every amino acid after mutation is wrong
65
Examples of asexual reproduction in prokaryotes
Binary fission of bacteria, where the parent organism divides equally in two.
66
Definition of homologous pairs.
Pairs of chromosomes where each chromosome contains DNA instructions for the same traits, but the exact instructions can differ.
67
Meiosis
A type of cell division that reduces the chromosome number by half, creating four haploid cells (sperm or egg).
68
The union of two haploid gametes restores the diploid number of chromosomes.
This is called fertilization. Normal somatic cells should have an even number of chromosomes.
69
What criteria are used to arrange chromosomes in a karyogram?
Chromosomes are arranged based on length/size, banding patterns, and position of centromere.
70
Nondisjunction
The most common error in meiosis where chromosomes fail to separate in Anaphase I or II, leading to abnormal numbers of chromosomes in gametes.
71
Turner's Syndrome
A sex chromosomal disorder associated with females. Causes offspring to inherit only one X chromosome (genotype = XO). Female is sterile due to underdeveloped sex organs. AKA Fragile X syndome
72
Which parent determines the sex of the offspring?
Father determines the sex of the offspring by donating either an X or a Y chromosome. If the offspring receives an X from the father, it is female. If it receives a Y, it is male.
73
Normal meiotic division results in gametes with how many chromosomes in humans?
23 chromosomes (n = 23)
74
Purpose of displaying all chromosomes in a cell
Examine for abnormalities.
75
Trisomy
Trisomy is the presence of three copies of a chromosome after fertilization. This condition can lead to genetic disorders such as Down syndrome.
76
Aneuploidy
A condition where gametes have 1 extra or 1 missing chromosome due to nondisjunction.
77
Amniocentesis
Involves collecting amniotic fluid to sample fetal cells, typically for use in creating a karyogram.
78
Nondisjunction in Meiosis I results in gametes with how many chromosomes in humans?
24 chromosomes (n + 1) or 22 chromosomes (n - 1)
79
Amount of chromosomes in normal human somatic cells
Humans have 46 chromosomes (diploid: 2n).
80
Klinefelter syndrome
Klinefelter syndrome (47,XXY) ; resulting male is sterile.
81
Down Syndrome
A condition where there are 3 copies of chromosome #21 (trisomy).
82
Karyogram
A micro-photograph of all chromosomes sorted and rearranged by size and position of the centromere.
83
Chromosomal mutations
Chromosomal mutations during meiosis can include changes to the structure of the chromosome. Types of chromosomal structural mutations: Deletion, Duplication, Inversion, Translocation.
84
Klinefelter’s Syndrome is associated with which biological sex?
Males
85
Monosomy
Monosomy is the presence of one copy of a chromosome after fertilization. This condition can lead to genetic disorders such as Turner's syndrome
86
Effects of Nondisjunction in Meiosis II
2 gametes are normal and 2 are affected. -2 will be n (normal) -1 will be n+1 (have an extra chromosome) -1 will be n+1 (missing a chromosome)
87
What causes an extra X chromosome in Klinefelter’s Syndrome?
Nondisjunction during meiosis
88
Karyotype
A property of a cell describing the amount, type, and description of chromosomes present in the nucleus. Example: normal female karyotype is 46,XX.
89
Effects of Nondisjunction in Meiosis I
All 4 gametes will be abnormal -2 will be n+1 (have an extra chromosome) -2 will be n+1 (missing a chromosome)
90
Karyotype information
- Biological sex (male or female) - Irregular numbers of chromosomes - Mutations in the chromosomes
91
How a karyogram is made
1. Collect sample: - Fetus: amniotic fluid or placenta piece - Newborn: white blood cells 2. Separate dividing & non-dividing cells using chemicals 3. Culture the dividing cells 4. Add chemical to stop cell division at metaphase 5. Lyse the cells 6. Stain the chromosomes 7. Analyze
92
Possible chromosomal patterns in Klinefelter’s Syndrome
XXY, XXXY, or XXXXY
93
Examples of disorders from non-disjunction:
Down Syndrome (trisomy 21), Klinefelter Syndrome (XXY), Turner’s Syndrome (monosomy X).
94
Nondisjunction in Meiosis II results in gametes with how many chromosomes in humans?
24 chromosomes (n + 1), 22 chromosomes (n - 1), or 23 chromosomes (n)
95
Chorionic Villus Sampling (CVS)
Involves collecting cells from the placenta during pregnancy, typically for use in creating a karyogram.
96
autosomes vs sex chromosomes
In humans, the first 22 pairs of chromosomes are autosomes (chromosome 1-44) and the 23rd pair are the sex chromosomes (XX for female, XY for male)
97
Why do zygotes formed from Non-disjunction in gametes lead to disorders?
If a zygote is formed from a gamete that has experienced a non-disjunction event, the resulting offspring will have extra or missing chromosomes in every cell of their body

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