Chapter 8 DNA and Meiosis

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  • Created by: Kate
  • Created on: 17-02-14 13:03
What three components make up a nucleotide?
Phosphate, Deoxyribose sugar, Organic Base
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Cytosine (C) always pairs with what base?
Guanine (G)
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Adenine (A) always pairs with what base?
Thymine (T)
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How many hydrogen bonds form between Cytosine and Guanine?
3
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How many hydrogen bonds form between Adenine and Thymine?
2
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Which base contains Nitrogen?
The organic base
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In a strand of DNA, the percentage of Adenine is 27%, give the percentage of the other four bases.
Thymine: 27% Guanine: 23% Cytosine: 23%
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What is the definition of a gene?
A section of DNA on a chromosome that contains information to code for one or more polypeptides
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What is the triplet code?
The theory that three bases code for one amino acid
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What is an intron?
A section/or sections of DNA that do not code for amino acids
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What is a codon?
The coding sequence that three bases makes one amino acid
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Define 'Homologous Pair'
Homologous Pair: a pair of chromosomes, one maternal, one paternal. They are not identical-they have the same gene loci which determines the same/similar features.
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Define 'Sister Chromatids'
Sister Chromatids: two identical molecules of DNA attached to one another by the centromere
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Define 'Diploid number of chromosomes'
cells that contain two sets of chromosomes in their nucleus
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Define 'Haploid number of chromosomes'
cells that only contain a single copy of each chromosome (eg gametes)
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Why is it important for gametes (produced by meiosis) to have haploid number of chromosomes?
So that the diploid number may be restored during fertilisation
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What is the difference between Meiosis and Mitosis?
Meiosis produces four daughter cells with haploid number of chromosomes and has genetic variations. Mitosis produces 2 identical clone daughter cells with diploid number of chromosomes-no genetic variation.
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Describe what happens during Interphase 1 (of Meiosis 1)
Normal cellualar activities, cell growth. DNA replicates so that for each chromosome, there is a sister chromatid attached to the centromere
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Describe what happens during Prophase 1 (of Meiosis 1)
Chromosomes condense and become visible. Nucleolus and Nuclear Envelope fades. Centrioles duplicate and Spindles begin to form.
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Describe what happens during Metaphase 1 (of Meiosis 1)
Spindles have completley formed and reached poles, they attach to centromeres of sister chromatids. Chromosomes line up on the equator - Bivalents are linked at chiasmata
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Describe what happens during Anaphase 1 (of Meiosis 1)
Microtubules of the spindles pull bivalents (homologous pairs) apart towards opposite poles
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Describe what happens during Telophase 1 (of Meiosis 1)
Chromosomes reach opposite poles and nuclear envelope begins to reform around them. Two new cells (formed by cytocinesis) with diploid number of chromosomes.
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Describe what happens during Prophase 2 (of Meiosis 2)
Chromatids condense. Centrioles duplicate and begin to move towards poles.
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Describe what happens during Metaphase 2 (of Meiosis 2)
Nuclear envelope disappears. Spindles have completely formed and attached to centromere of sister chromatids. Sister chromatids line up on the equator.
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Describe what happens during Anaphase 2 (of Meiosis 2)
Sister chromatids are pulled apart by the microtubules of the spindle to opposite poles.
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Describe what happens during Telophase 2 (of Meiosis 2)
Nuclear envelope forms round four new single chromatids/chromosomes. Cytocinesis forms four new daughter cells with haploid number of chromosomes.
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What is cytocinesis?
The process in which the cell actually divides, to produce new cells.
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What are bivalents?
Where homologous pairs are joined by the chiasmata.
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State two outcomes of Meiosis
Genetic Variation and 4 haploid cells
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State the two ways in which genetic variation may occur during meiosis
Independent segregation/assortment and crossing over
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Describe the process of Independent Segregation/Assortment
During Metaphase 1 (of meiosis 1) the chromosomes line up randomly on the equator, this means that the combination of chromosomes that go into the daughter cell at meiosis 1 is also random
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Describe the process of Crossing Over
During Metaphase 1 (of meiosis 1) the chromatids become twisted around one another. This may create tension causing a portion of chromatid to break off. Equivalent portions of chromatid break off and recombine with its homologous partner.
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What is the function of the spindle?
They attach to the centromere of sister chromatids and pull them apart during Anaphase.
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If the Dog diploid number of chromosomes is 78, what is the haploid number?
39
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What is an allele?
One of the different forms of a particular gene
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How does the DNA of a Prokaryotic cell differ from a Eukaryotic cell?
Prokaryotic Cells: DNA is smaller, forms a circle and is not associated with proteins. Eukaryotic Cells: DNA is larger, linear and occurs in association with proteins to form structures called chromosomes.
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What is the function of the protein found in chromosomes?
The proteins hold the DNA in chromosomes in position,
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How is it that DNA (of considerable length) is able to fit inside a chromosome?
It is highly coiled and looped and so is condensed into a single chromosome.
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Other cards in this set

Card 2

Front

Cytosine (C) always pairs with what base?

Back

Guanine (G)

Card 3

Front

Adenine (A) always pairs with what base?

Back

Preview of the front of card 3

Card 4

Front

How many hydrogen bonds form between Cytosine and Guanine?

Back

Preview of the front of card 4

Card 5

Front

How many hydrogen bonds form between Adenine and Thymine?

Back

Preview of the front of card 5
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