Meiosis Flashcards
What is nucleotide excision repair?
Nucleases cut the DNA at the mismatched pair and the damaged DNA is removed
DNA polymerase fills the gaps with proper nucleotides
Ligase ligates it back together using undamaged DNA as the template
What are histones?
Proteins that pack the chromatin
In interphase, the chromatin is in what form?
Heterochromatin (super tightly packed)
When being transcribed during gene expression, chromatin is in what form?
Euchromatin (looser)
Heredity
The transmission of traits from one generation to the other
Variation is due to ______
Combinations of alleles
Genetics is the study of _______ and ___________
Heredity and heredity variation
Genes
The unit of heredity
If it is inherited and causes a trait it is ______
A gene
What is a locus?
The gene’s specific location on a chromosome
Gametes
Reproductive cells that pass on genetic information
What are the two ways organisms can reproduce?
- Asexual reproduction (Mitosis)
-Cells are clones to the parents - Sexual reproduction (Meiosis)
-Cells are genetically similar but not identical to parents
Chromosomes 1-22 are __________
Autosomal chromosomes
X and Y are the ________
Sex chromosomes
What is a karyotype?
A picture that arranges chromosomal pairs from longest to shortest
Are gametes haploid or diploid?
Haploid (n=23)
Meiosis takes a ________ and produces ___________
Diploid (2n=46) germ cell
4 haploid gamete cells
Fertilization merges?
Two haploid gametes to form a diploid zygote (2n=46)
Are sister chromatids exact copies of each other?
Yes
Homologous recombination
The swapping of bits of homologous chromosomes
Homologous chromosomes
Pairs of chromosomes in a diploid organism that have similar genes, that are not not necessarily identical.
How do we count chromosomes?
By the number of centromeres
Meiosis l separates ______
Homologous chromosomes (2n-1n)
Where does homologous recombination occur?
Meiosis l
Meiosis ll separates __________
Sister chromatids (n -n)
When does crossing over occur?
Prophase l
Recombination steps
- In crossing over (recombination) the sister chromatids are held together by ______?
- DNA strand breaks are made by __________
- Proteins come in and hold the two non-sister chromatids together starting from _________
- The ________ disappears but the chromosomes are still held together
Cohesins
Proteins on non-sister chromatids
The synaptonemal complex (zipper)
Synaptenomal complex
What is synapsis?
The fusion of chromosome pairs
On average, how many cross over events are there per homologous chromosome pair?
2-3 but there can be 0
Metaphase l difference from mitosis?
Homologous chromosome pairs line up at the metaphase plate
Anaphase l difference from mitosis?
The sister chromatids remain together
Telophase l and cytokinesis difference from mitosis?
Each half of the cell has a haploid set of duplicated chromosomes
Cytokinesis is normal
Do chromosomes duplicate again when going into meiosis ll?
No
Prophase ll difference from mitosis?
Each cell is haploid
Metaphase ll difference from mitosis?
Each cell is haploid and the two sister chromatids are not genetically identical
Is anaphase ll and anaphase in mitosis the same?
Yes
What is the name for the shortening of spindle fibres?
Depolymerisation
Telophase ll and cytokinesis differences from mitosis?
Production of 4 genetically distinct haploid daughter cells whereas mitosis produces two identical daughter cells
What are the sources of genetic variation from sexual reproduction?
- Crossing over
- Independent assortment of chromosomes
- Random fertilization (8.4 million different chromosomal combinations from each sperm and egg)
Why do sexual reproduction?
Produces more genetic and phenotypic variation in a population
Despite it requiring more energy, it is more useful in ensuring survival
