Genetics: Chromosomes Part 2 Flashcards
Why is it important to study the processes controlling cell division?
So we can try and fix or manipulate these processes for our own benefits. For example, we could try and improve regenerative mechanisms
What is apoptosis? When does it occur
Programmed cell death. It occurs when it fails a checkpoint and has damaged chromosomes
How are telomeres extended in the germ cells?
There’s a complex called telomerase which adds telomeres to the chromosomes
Meiosis produces _ gametes while mitosis produces _ daughter cells
4, 2
What is the cell cycle?
The sequence of events from a cell’s formation until its own division into two daughter cells.
What phases are part of the cell cycle?
Interphase and the cell division phase (mitosis and cytokinesis)
What is the general process for mitosis? What are the 6 official phases?
Duplicate chromosomes and separate the duplicated chromosomes so that each cell receives one copy.
Interphase, prophase, prometaphase, metaphase, anaphase, telophase/cytokinesis
What phases does interphase consist of?
Growth 0/1, S phase (chromosome duplication), Growth 2 (check for damaged or unduplicated DNA)
The cell cycle is under tight ________ in eukaryotes. This causes several __________ in the cycle that send stop or go signals
regulation, checkpoints
What sort of checkpoints exist to stop the cell cycle?
- Check for favourable environmental conditions
- Check for DNA damage or stalled replication forks
- Check for damaged or unduplicated DNA
- Check for chromosome attachment to mitotic spindle
What helps the cell actually split in animal and plant cells?
Animal: Contractile ring (which makes the cleavage furrow)
Plant: Golgi Vesicles and cell plates
Some organisms like _________ can regenerate amputated limbs via activation of _____ _______ to supply new cells in the growing limb
salamanders, cell division
How do hydras reproduce?
A mass of cells divide by mitosis to form a bud, which developers into a small hydra that detaches from the parent
What is asexual reproduction?
Reproduction from oneself
What is cancer often caused by?
A series of mutations in chromosomes DNA
Why do cancer cells reproduce uncontrollably?
Cancer cells do not respond normally to the cell cycle control system
What are telomeres? What are they used for?
Sequences of DNA capping off chromosome ends. They are essential for DNA replication, is the enzyme attaches to them.
What happens to telomeres as cells divide? What are the implications of this?
Telomeres get shorter each time a cell divides. Once they are short enough, the prevent cell division, which leads to senescence and possibly oncogenic transformation of cells
Learning how plants clone themselves via mitosis can enable plant breeders to _______ these plant propagation techniques
optimise
What did Thomas Hunt Morgan’s work with fruit flies uncover in relation to genetic diversity?
It showed recombination, and how genes on the same chromosome could recombine during meiosis to produce novel phenotypes
Describe Thomas Hunt Morgan’s work that allowed him to discover recombination
He noticed that certain traits were linked and always inherited together: Grey/Long vs Black/Short
Both these traits are carried on the X-chromosome. Since the fly inherits one whole chromosome from mother and father, one would expect that the traits are inherited together.
However, he noticed some flies with Grey/Short and Black/Long
What does sexual reproduction depend on?
Meiosis and fertilization
What is meiosis?
The process in which haploid gametes are created from diploid cells
Describe the human life cycle for the gametes.
- Meiosis occurs to produce haploid gametes
- Fertilisation combines the haploid paternal and maternal genomes to produce a diploid zygote
- The diploid zygote undergoes mitosis to produce identical diploid cells
All adult body cells are _______ with two _________, for a total of 46 chromosomes
diploid, genomes
All gametes are _______ with one genome for a total of 23 chromosomes
haploids
The diploid zygote in human reproduction has __ chromosomes
46
The haploid gametes generated from meiosis are ________ unique from each other and from the parent cell
genetically
Describe the process of meiosis?
- Chromosomes duplicate
- Duplicated pair of homologous chromosomes align together (this is important, as crossover can happen here). These are called sister chromatids. (4 chromosomes total)
- Homologous chromosomes separate into 2 cells (2 * 2 chromosomes total)
- Sister chromatids separate (4 * 1 chromosomes total)
What are 3 ways novel combinations of different alleles can be formed in the offspring?
- Meiosis 1: Crossing over between maternal and paternal chromosomes
- Meiosis 2: Independent assortment of each homologous chromosome pair
- Fertilisation and combining maternal and paternal genomes
Why does independent chromosome assortment increase diversity?
Chromosome pairs from mom and dad are randomly sorted into daughter cells, resulting in 4 possible combinations in gametes
What is the total number of chromosome combinations that can appear in the gametes due to independent assortment?
2^23 = around 8.4 million
How many chromosome combinations are possible with independent assortment and fertilization?
8.4m * 8.4m = >70 trillion combinations
What is recombination?
When 2 homologous chromosomes swap genes`and create new combinations of alleles
Alfred Henry Sturtevant noticed that the frequency of __________ was related to the distance between genes
recombination
What is a linkage map?
It shows gene positions on chromosomes
What is a centiMorgan?
A unit for measuring genetic linkage. It is the distance between chromosome position for which the expected average number of crossovers in a single generation is 0.01
Why do genes that are further apart more likely to be recombined?
They are more separated, so when the gene splits, it’s less likely they will be part of the same chunk that split.
