Meiosis And Mutations Flashcards
What is meiosis?
Meiosis is a type of cell division that reduces the chromosome number by half, resulting in four haploid cells.
Fill in the blank: Meiosis consists of two rounds of division called _____ and _____.
meiosis I and meiosis II
What is the end product of meiosis?
Four genetically different haploid cells.
Multiple Choice: During which phase does crossing over occur?
Prophase I
What is the significance of crossing over in meiosis?
It increases genetic diversity among the offspring.
What happens during anaphase I?
Homologous chromosomes are pulled apart to opposite poles of the cell.
True or False: In meiosis II, sister chromatids are separated.
True
What is the role of the spindle fibers during meiosis?
They help separate chromosomes during cell division by pulling them to the opposite ends of the cell by their centromere.
Fill in the blank: The genetic variation in meiosis is primarily due to _____ and _____.
crossing over and independent segregation
What is independent segregation? And how does it happen?
The random distribution of maternal and paternal chromosomes into gametes during meiosis.
It happens when the pairs are separated in meiosis I and it is completely random which chromosome from each pair ends up in which daughter cell.
How many chromosomes does a human gamete contain?
23
True or False: Meiosis occurs only in reproductive cells.
True
Fill in the blank: The _____ phase of meiosis I is crucial for genetic diversity.
prophase I
What is the term for the exchange of genetic material between homologous chromosomes?
Crossing over
Which stage of meiosis involves the formation of gametes?
Meiosis II
What are gametes?
Gametes are the reproductive cells (sperm and eggs) that are produced through meiosis.
True or False: All organisms undergo meiosis.
False
Fill in the blank: The final result of meiosis is _____ haploid cells from one diploid cell.
four
What occurs during fertilisation?
A haploid sperm fuses with a haploid egg, forming a diploid cell.
What is the chromosome composition of the cell formed after fertilisation?
Half the chromosomes are from the father and half are from the mother.
Is fertilisation random or selective?
Fertilisation is random.
What does random fertilisation produce?
Zygotes with different combinations of chromosomes from both parents.
Fill in the blank: During fertilisation, a haploid sperm fuses with a haploid _______.
[egg]
What happens before meiosis starts?
The DNA unravels and replicates so there are two copies of each chromosome called chromatids
What is a mutagenic agent?
A factor that increases mutations e.g UV light, ionising radiation or toxins.
What is a mutation?
A mutation is a change in the DNA sequence of an organism.
True or False: All mutations are harmful.
False
What is a point mutation?
A point mutation is a change in a single nucleotide in the DNA sequence.
What is a frameshift mutation?
A frameshift mutation is caused by the insertion or deletion of nucleotides that shift the reading frame of the genetic code.
What is a silent mutation?
A silent mutation is a change in the DNA sequence that does not affect the amino acid sequence of the protein.
Multiple Choice: Which type of mutation results in a premature stop codon? A) Missense B) Nonsense C) Silent D) Inversion
B) Nonsense
Fill in the blank: Mutations can lead to genetic _____, which is the variety of different genetic traits within a population.
diversity
What is a missense mutation?
A mutation that results in a different amino acid.
What is a gene mutation?
The change of one base in the DNA sequence that can lead to a change in the amino acid sequence of the polypeptide which can alter the function of a protein
What is a chromosomal mutation?
A spontaneous change in the structure of number of whole chromosomes.
How does a chromosomal mutation usually occur?
Due to a fault during meiosis when making gametes and chromosomes fail to properly separate. It can lead to polyploidy organisms.
What is a polyploidy organism?
Changes in the number of whole sets of chromosomes in an organism.
How are sister chromatids created?
From DNA replication
What happens in the first division of meiosis?
Homologous pair of chromosomes separate with one in each daughter cell so there is a haploid number
How is genetic variation produced in meiosis?
Crossing over and Independant segregation and mutations
What is an event that occurs in division 2 but not division 1?
Sister chromatids separate by division of the centromere.
Why would all cells of the body have a non disjunction mutation of chromosomes?
All cells are derived from a single cell by mitosis.
Mitosis produces genetically identical cells.
Explain how a gene mutation could result in a new protein
Change in the base sequence as a result of deletion/substitution/addition
Results in a change in amino acid sequence so a change in tertiary structure of protein
How is the chromosome number halved during meiosis?
In the first division of the cell, the homologous chromosomes split and one from each pair goes to each daughter cell
Describe the process of crossing over and how it increases genetic diversity
The alleles in the Non-sister chromatids in homologous pairs are exchanged to produce a new combination of alleles. This happens when the chromatids twist and entangle.
What is a haploid cell
Gametes have one copy of chromosomes (half normal number)
What is a diploid cell
Normal body cell, contains 2 chromosomes one maternal one paternal. Full set of chromosomes
