Inheritance paper 2 review Flashcards
Outline the reason for diploid organisms producing haploid cells by meiosis?
Meiosis is used for sex cells (gametes) and each gamete needs 23 chromosomes to pass on which is why diploids divide to produce haploid cells
Explain how non-disjunction during meiosis can lead to down syndrome?
Non-disjunction is completely random and occurs when the 21st pair of homologous chromosomes fails to separate during anaphase resulting in down syndrome
Stage of meiosis where chiasmata formation may occur?
P1 during cross over
Explain gene linkage and its effects on inheritance
Gene linkage is when 2 or more genes are extremely close together in same Chromsomes meaning they are inherited together
Effects: Crossing over difficult, less genetic variation, stronger link
Outline how nucleosome affect the transcription of DNA
Methylation can happen on histones tightning the DNA making it less likely to be transcribed
Enzyme that copies a DNA sequence
RNA polymerase
Non coding DNA at start of a gene
Promoter region
Explain the role of lactose in the expression of the gene for lactase production
When lactose is produced it attaches to lac repressers which detaches it allowing RNA polymerase to synthesize lactase which controls the level of lactose, lac repressor reattaches when lactose levels are down
One reason that identical twins may show different methy;action patterns as they grow older?
Environmental factors - environment they grow in alters methylation patterns as they grow older
How is sex determined in humans?
When a zygote is created it takes a chromosome from each parent. The mother only has x chromosomes to offer while the father can give x or y. If X is taken from the father it is a girl but if y is taken it is a boy meaning the gender is determined by the father
Explain how sexual reproduction gives rise to genetic variation?
Variation in sexual reproduction mainly happens in prophase 1 of meiosis when crossing over occurs
