Chrom and Gam Flashcards
What is the defining feature of all evolving living organisms?
ability to reproduce
What are the requirements for genes to be functional?
→replicate
→separate its 2 copies at mitosis- eliminating mutations
→maintain itself between generations
How can the same gene be specific?
→ by having alternative promotors
Give an example of a protein that uses different promotors depending on the tissue
→CYP19A1
What are the products of alternative splicing called?
→isoforms
How can the protein be modified once made?
→Post-translational modification eg phosphorylation,
→Glycosylation i.e. adding on carbohydrates to protein, making protein more stable and soluble
What happens to FSH as women age?
→more variants of FSH which are not as effective
What are the DNA requirements for sexual reproduction?
→Fusion of haploid cells (gametes) to create unique diploid progeny
What are the advantages of sexual reproduction?
→Prevents the accumulation of genetic mutations
→Increase in genetic diversity
→Maintenance occurs because of the advantage of genetic variability
What are the numbers of gene in the X and Y chromosomes?
X chromosome → 1000 working genes
Y chromosome → 86 working genes
What is a gamete?
→a haploid cell specialised for sexual fusion
What are gametes formed from?
→formed from germ line cells: primordial germ cells
→progenitors of both sperm and egg that migrate into the gonad and then differentiate to either male or female gametes
What happens to the two chromosomes during S-phase as replication happens?
→remain attached to each other
What is a chromatin?
→uncondensed form of DNA
What happens in prophase?
→chromatin condense to form chromosomes as DNA wraps around histones
→when DNA is condensed it cannot be replicated and gene activity is shut down
→nuclear membrane begins to break down
→mitotic spindle forms (duplicated during interphase)
What happens in metaphase?
→mitotic spindles attach to the chromosomes at the equator
What happens in anaphase?
→the sister chromatids of each chromosome begin to separate
→spindle fibres pull chromosomes to each pole
What happens in telophase?
→a nuclear envelope forms around each group of chromosomes at each pole
→mitotic spindle disassembles
What are the two important sources of genetic variation?
→crossing over recombination during prophase I
→independent assortment during metaphase I
What is a difference between meiosis I and meiosis II?
→no interphase or replication in meiosis II
Why is meiosis advantageous?
→random distribution of male and female homologous chromosomes
→chromosomal crossing over
→keeps the number of chromosomes constant between generations
Compare mitosis and meiosis
mitosis
→one cell division
→produces two diploid cells
→somatic cells
→growth and repair
→no Exhange of genetic material
→daughter cells genetically similar
Describe crossing over
→Corresponding pieces of chromatids of maternal and paternal homologues (non-sister chromatids) are exchanged during synapsis when the homologues are aligned side by side.
Each of the affected chromatids has a mixture of maternal and paternal genetic information
Why does crossing over not occur between X and Y chromosomes?
→They are hemizygous to each other & so recombination proved harmful
→PAR allows the X & Y chromosomes to pair and properly segregate during meiosis in males
