IB BIOLOGY GENETICS ALREADY RATED A+
1. What is a gene?
- Answer: A gene is a heritable unit that dictates a specific trait or characteristic in an organism.
2. How is an allele defined?
- Answer: An allele is a specific variant of a gene that differs from other alleles by one or a few
nucleotide bases and occupies the same locus as those alleles.
3. What constitutes a genome?
- Answer: The genome encompasses the complete set of genetic material found within an organism.
4. What is meant by gene mutation?
- Answer: A gene mutation refers to any alteration in the sequence of bases within a gene.
5. Explain base substitution.
- Answer: Base substitution is the simplest form of mutation, in which one nucleotide base in a gene is
replaced by another. An example of this is sickle cell anemia.
6. Define meiosis.
- Answer: Meiosis is a type of cell division where a diploid nucleus undergoes reduction to create
haploid nuclei.
7. What are homologous chromosomes?
- Answer: Homologous chromosomes are pairs of chromosomes that carry the same genes at the same
loci, though they may have different alleles for those genes.
8. Describe random orientation in meiosis.
, - Answer: Random orientation occurs during prophase I when each pair of homologous chromosomes
aligns randomly, influencing the genetic variation of gametes.
9. What is non-disjunction?
- Answer: Non-disjunction is an error in meiosis where chromosomes that should separate fail to do so
and both move to the same pole of the cell.
10. What is karyotyping?
- Answer: Karyotyping involves the arrangement of chromosomes into pairs based on size. It is often
performed using cells obtained through chorionic villus sampling for prenatal diagnosis of chromosomal
abnormalities.
11. What happens during prophase I?
- Answer: In prophase I, chromosomes supercoil, homologous chromosomes (bivalents) pair through
synapsis, and crossing over occurs, leading to the formation of chiasma. The centrioles migrate to
opposite poles, and the nuclear membrane begins to disintegrate.
12. What occurs during metaphase I?
- Answer: During metaphase I, spindle microtubules attach to the centromeres, and the bivalents align
along the equatorial plane.
13. Describe anaphase I.
- Answer: Anaphase I involves the separation of the two chromosomes of each bivalent, moving them
to opposite poles. This halving reduces the chromosome number, and if crossing over has occurred, the
resulting chromosomes consist of two sister chromatids that may not be identical.
14. What takes place during telophase I?
- Answer: In telophase I, nuclear membranes reform, and the cell divides to produce two haploid cells.
15. What characterizes prophase II?
- Answer: Prophase II features chromosome supercoiling similar to the previous prophase, but since
there are no homologous chromosomes to pair, there is no crossing over.
1. What is a gene?
- Answer: A gene is a heritable unit that dictates a specific trait or characteristic in an organism.
2. How is an allele defined?
- Answer: An allele is a specific variant of a gene that differs from other alleles by one or a few
nucleotide bases and occupies the same locus as those alleles.
3. What constitutes a genome?
- Answer: The genome encompasses the complete set of genetic material found within an organism.
4. What is meant by gene mutation?
- Answer: A gene mutation refers to any alteration in the sequence of bases within a gene.
5. Explain base substitution.
- Answer: Base substitution is the simplest form of mutation, in which one nucleotide base in a gene is
replaced by another. An example of this is sickle cell anemia.
6. Define meiosis.
- Answer: Meiosis is a type of cell division where a diploid nucleus undergoes reduction to create
haploid nuclei.
7. What are homologous chromosomes?
- Answer: Homologous chromosomes are pairs of chromosomes that carry the same genes at the same
loci, though they may have different alleles for those genes.
8. Describe random orientation in meiosis.
, - Answer: Random orientation occurs during prophase I when each pair of homologous chromosomes
aligns randomly, influencing the genetic variation of gametes.
9. What is non-disjunction?
- Answer: Non-disjunction is an error in meiosis where chromosomes that should separate fail to do so
and both move to the same pole of the cell.
10. What is karyotyping?
- Answer: Karyotyping involves the arrangement of chromosomes into pairs based on size. It is often
performed using cells obtained through chorionic villus sampling for prenatal diagnosis of chromosomal
abnormalities.
11. What happens during prophase I?
- Answer: In prophase I, chromosomes supercoil, homologous chromosomes (bivalents) pair through
synapsis, and crossing over occurs, leading to the formation of chiasma. The centrioles migrate to
opposite poles, and the nuclear membrane begins to disintegrate.
12. What occurs during metaphase I?
- Answer: During metaphase I, spindle microtubules attach to the centromeres, and the bivalents align
along the equatorial plane.
13. Describe anaphase I.
- Answer: Anaphase I involves the separation of the two chromosomes of each bivalent, moving them
to opposite poles. This halving reduces the chromosome number, and if crossing over has occurred, the
resulting chromosomes consist of two sister chromatids that may not be identical.
14. What takes place during telophase I?
- Answer: In telophase I, nuclear membranes reform, and the cell divides to produce two haploid cells.
15. What characterizes prophase II?
- Answer: Prophase II features chromosome supercoiling similar to the previous prophase, but since
there are no homologous chromosomes to pair, there is no crossing over.
