9.2 Sexual reproduction Flashcards
What is sexual reproduction?
Involves the combination of genetic information from male and female sex cells to form a new unique individual.
What are multicellular organisms composed of?
- Somatic cells
- Germ cells (sex cells)
What are somatic cells?
- Are all the cells other than gametes (sex cells)
- Are diploid, which means they make two copies of each chromosome.
What is meiosis?
The process of cell division that produces gametes.
What happens during Prophase I?
- Nuclear membrane disappears
- Chromosomes become visible
- Chromosomes pair up with their homologous partner
- They cross over each other
- Centrioles move to poles of the cell
How many chromosomes are there in diploid human cells?
46
How many chromosomes are there in haploid human cells?
23
What are gametes?
Sex cells:
- Sperm (male)
- Eggs (female)
What is the importance of the chromosomes crossing over during Prophase I?
It adds variation since the DNA of both the male and female are being randomly exchanged.
What are the stages of meiosis?
- Interphase I
- Prophase I
- Metaphase I
- Anaphase I
- Telophase I and Cytokinesis
- Prophase II
- Metaphase II
- Anaphase II
- Telophase II and cytokinesis
What is Spermatogenesis?
The process of meiosis in males that produces sperm
What is Oogenesis?
The process of meiosis in females that produces eggs
Where in the body does meiosis occur?
In the testes and ovaries
How many divisions are there in meiosis?
2
How many daughter cells are produced in meiosis?
4
What types of cells are the daughter cells produced by meiosis?
Gametes
During what phase of meiosis are the chromatids separated?
During Anaphase II
Name 4 advantages of sexual reproduction:
- Long-term evolutionary potential
- Unfavourable genetic variation is eliminated from the population more efficiently
- Generates genetic variation and selects for beneficial genetic variation more efficiently
- Populations are better able to adapt to and survive changing environmental conditions
Name 3 disadvantages of sexual reproduction:
- Slower reproductive rate
- Recombination can break apart beneficial genomic combinations and introduce deleterious variation to the population
- Energetically costly
What can happen if meiosis goes wrong?
- The sperm or egg produced (gamete) could have the wrong number of chromosomes.
- If the gamete is used in fertilisation the resulting offspring (zygote) will have an abnormal number of chromosomes in each cell.
What is meiosis referred to when it has gone wrong?
Anenploidy
What is non-disjunction?
When gametes are missing a chromosome or have an extra chromosome, which is caused by a chromosome failing to separate during meiosis.
eg. Down syndrome
What is the effect of having 2 Y chromosomes?
It can lead to higher levels of testosterone
What are the 4 types of damage to chromosomes structures?
- Deletions
- Translocation
- Duplication
- Inverson
What is polyploidy?
Damage meiosis which can cause there to be an extra complete set of chromosomes.
