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genetics chapter 4
the sex chromosomes
| Question | Answer |
|---|---|
| how do sex chromosomes differ from other chromosomes? | sex chromosomes determine the biological sex of the individual, no other chromosomes distinguish that |
| what happens during Klinefelter syndrome? | males with two X chromosomes and one Y chromosome that results in abnormalities collectively |
| what happens during turner syndrome? | females have an X chromosome but no secondary sex chromosome |
| what is the SRY gene? where is it located, and what does it do? | a region on the Y chromosome that determines maleness; the region is on the short arm of the chromosome, and the protein activates testes development |
| what are pseudoautosomal regions? | the two ends of the x and y chromosomes that contain about 30 genes, and they cross over during male meiosis |
| how do the x and y chromosomes differ? | the x chromosome is much larger than the y chromosome and the majority of its genes have nothing to do with sex. |
| why do x and y chromosomes still pair during meiosis? | it is the PARs that allow these chromosomes to pair during meiosis even if they are very dissimilar |
| how is sex determined in humans? | XX is female, and XY is male. the presence of a Y chromosome determines the male sex. |
| how is sex determined in fruit flies? | the number of X chromosomes rather than the presence or absence of the Y chromosome |
| what other combinations of sex chromosomes can determine sex in different species? | moths: females are XX and males are XO; nematodes: males are XO but XX is not female because they are self fertilizing hermaphrodites producing both egg and sperm |
| what is gametogenesis? | biological process of creating mature sex cells through mitosis and meiosis |
| what is oogenesis? | process of creating the egg cell, or female gamete |
| what is the difference between oogonia and oocytes? | oogonia are cells in the ovaries that divide by mitosis to create more oogonium and eventually oocytes, whereas oocytes are cells that go through meiosis to create mature egg cells. |
| during what stage of like are oocytes produced? | meiosis I (occurring before birth and arresting at prophase I) and meiosis II (arresting at metaphase II) |
| how are ovum produced during meiosis? | oogenesis; which is two rounds of asymmetric cell division during meiosis |
| how many eggs are produced from an oogonia? | 1 mature egg cell |
| what is a polar body? | cells that bud off of an oocyte at the two meiotic divisions but do not produce ova. |
| aneuploidy | condition in which an individual has an abnormal amount of chromosomes compared to the original amount. |
| why does age increase the risk of down syndrome? | there could be errors in meiotic segregation in older eggs |
| what is spermatogenesis? | the production of sperm |
| how does the production of sperm differ than that of egg production? | Unlike primary oocytes, primary spermatocytes undergo symmetrical meiosis I, producing two secondary spermatocytes, each of which undergoes a symmetrical meiosis II |
| during what stage of life are spermatids produced? | during the male's reproductive age, beginning at puberty and continuing through adulthood |
| what is a sex-linked trait? | characteristic controlled by a gene on the X or Y chromosome |
| how is a sex-linked trait passed on to future generations? | through the sex chromosomes |
| are X-linked recessive phenotypes more common in men or women? | men, since they only have one X chromosome |
| are X-linked dominant phenotypes more common in men or women? | women, since they have two X chromosomes, making them more likely to inherit the gene mutation |
| are Y-linked traits more common in men or women? | men, since women do not have a Y sex chromosome |
| how does the cell account for the fact that there are two X chromosomes (and hence twice as many X genes) in females than there are in males? | XX cells inactivate one of their X chromosomes about two weeks after fertilization |
| barr bodies | inactive x chromsome found in women |
| hemizygosity | state of having only one copy of a gene or chromosome segment instead of the usual 2 |
| sex-influenced trait | show up in both sexes, but the character of such traits may differ between the two sexes because of hormonal differences. |
| explain baldness | it is a sex-influenced trait in humans; males heterozygous for the balding allele lose hair in their 20s, whereas females heterozygous for balding do not show significant loss. |
Created by:
angievelasco