Flashcards in Gentetic variation (meiosis) Deck (16):
Species usually have different numbers of chromosome. Why are animals that are bred from two different species normally infertile?
1. (usually) an uneven number of chromosomes;
2. Chromosomes cannot pair
3. chromosomes are not homologous
4. meiosis cannot occur
Explain the role of independent segregation in meiosis.
1. To provide genetic variation;
2. Allows different combinations of
maternal and paternal chromosomes/
3. To produce haploid cells (half the
4. Allows homologous pairs to arrange randomly
at equator of cell
What is the importance of meiosis?
Halves chromosome number and restores diploid number at fertilisation
Describe and explain how selection will have affected the genetic diversity of sugar
1. Diversity reduced
2. As alleles have been chosen
Explain the appearance of a chromosomes
Due to DNA replication;
Joined by a centromere;
Explain how the gametes with the combinations of alleles Ef and eF have been produced.
Exchange of alleles between chromatids
explain how the production of gametes by meiosis contributes to this variation
Independent assortment/random alignment of (homologous) chromosomes;
Different combinations of maternal and paternal chromosomes;
Different combination of alleles/exchange of genetic material
Describe how crossing over occurs during meiosis I.
chromosomes in each homologous pair twist around each other;
chromatids break and rejoin to chromatid on sister chromosome
What is the biological importance of reducing the chromosome number when the cell
divides by meiosis?
Restoring diploid number
Describe 5 differences between meiosis and mitosis
1. Reduces the chromosome number
2. Homologous chromosomes associate in pairs
4. Two divisions → 4 offspring cells
5. Genetically different product
1. Maintains the same chromosome
number as in the parent nucleus
2. Homologues do not pair
3. No crossing-over;
4. One division → 2 offspring cells;
5. Genetically identical product;
Explain why the chances of inheriting a genetic disorder increase with a smaller community who only reproduce with people in that comunity
1. Less genetic diversity
2. As individuals only breed within group
3. Therefore Higher chance of inheriting allele
Suggest how a mutation can lead to the production of a protein that has one amino
loss of 3 bases
3 bases code a for 1 amino acid
Suggest how the production of a protein with one amino acid missing may lead to a
1.Change in sequence of bases
2. Therefore change in bonds formed in 1^0
3 . Therefore change in tertiary structure
4. Leading to a non-functional protein
Suggest four reasons why populations might show very low levels of genetic diversity.
1. genetic bottleneck
3. Population might have started with small
number of individuals
4. founder effect
How do changes to whole sets of chromosomes occur?
When organisms have more than the usual 2 sets of chromosomes. This is called polyploidy