3.4 Genetic information, variation and relationships between organisms - Genetic Diversity and Adaptation Flashcards
What is the definition of haploid?
Haploid (n) = one copy of each chromosome
Haploid cells are produced during meiosis.
What is the definition of diploid?
Diploid (2n) = two copies of each chromosome
Diploid cells contain pairs of homologous chromosomes.
What are the two key processes that introduce genetic differences during meiosis?
- Independent segregation of homologous chromosomes
- Crossing over between homologous chromosomes
These processes occur during meiosis and contribute to genetic variation.
What is meiosis?
Meiosis is the type of cell division that creates genetically different gametes.
It involves two nuclear divisions.
How many nuclear divisions occur during meiosis?
Two nuclear divisions
This results in four haploid daughter cells.
What occurs during interphase before meiosis?
The DNA and organelles double
Interphase is a preparatory stage before cell division.
What are the stages of meiosis referred to?
Meiosis I and Meiosis II
Each stage includes prophase, metaphase, anaphase, telophase, and cytokinesis.
What is independent segregation?
The process where homologous chromosomes are distributed randomly into daughter cells during meiosis.
This contributes to genetic variation.
What is crossing over?
The exchange of genetic material between homologous chromosomes during meiosis.
This process results in new combinations of alleles.
How many haploid daughter cells are produced at the end of meiosis?
Four haploid daughter cells
Each daughter cell contains a unique set of genetic information.
True or False: Mitosis results in genetically different daughter cells.
False
Mitosis produces genetically identical daughter cells.
Fill in the blank: Genetic variation can be introduced during meiosis, _____, and the random fertilisation of gametes.
[mutations]
Mutations are changes in the DNA sequence that can lead to genetic diversity.
What is crossing over?
Crossing over occurs in meiosis I when homologous pairs line up opposite each other at the equator, causing chromatids to twist and break, leading to genetic recombination.
This process results in new combinations of alleles in the gametes.
What happens to chromatids during crossing over?
Parts of the chromatids can become twisted around each other, causing pairs to break and recombine with another chromatid.
This leads to genetic recombination.
What is independent segregation?
In meiosis I, homologous pairs of chromosomes line up randomly at the equator, leading to the random separation of paternal and maternal chromosomes into daughter cells.
This process contributes to genetic variation.
How is the number of possible combinations of chromosomes in daughter cells calculated?
The number of combinations is calculated using the formula 2^n, where n is the number of homologous pairs.
In humans, there are approximately 8,388,608 combinations of chromosomes.
What are gametes?
Gametes are reproductive cells that carry genetic information and are produced through meiosis.
They include sperm and eggs in animals.
Fill in the blank: Crossing over occurs in _______.
meiosis I
True or False: Independent segregation leads to genetic diversity.
True
What is the result of crossing over during meiosis?
New combinations of alleles in the gametes.
This enhances genetic variation among offspring.
What does the term ‘homologous pair’ refer to?
A pair of chromosomes, one from each parent, that are similar in shape, size, and genetic content.
What is a chromatid?
A chromatid is one half of a duplicated chromosome, which is connected to its sister chromatid at the centromere.
What is a mutation in a gene?
A change in the base sequence of the DNA
Gene mutations can occur randomly during DNA replication.
What increases the likelihood of gene mutations?
Exposure to mutagenic agents
Examples include high energy radiation (UV light), ionising radiation (gamma rays and X rays), and chemicals (carcinogens such as mustard gas and cigarette smoke).