Term
| Most higher plants and animals are ___________ |
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Definition
| 1) Diploid (have 2 sets of homologous chromosomes) |
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Term
| The haploid chromosome number in humans is ___________ (___________ in a typical diploid cell) |
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Definition
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Term
| Lower vascular plants, such as ___________ and ___________, have a very (small/large) number of chromosomes. |
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Definition
1) Horsetails
2) Ferns
3) Large |
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Term
| Why do lower vascular plants have a very large number of chromosomes? |
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Definition
| 1) It is thought that because they are surviving members of evolutionary dead-ends (living fossils) their chromosomes have doubled several times (polypolidy) during the long time they have survived |
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Term
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Definition
| 1) The doubling of chromosomes |
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Term
| What are the 4 stages of the somatic cell cycle? |
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Definition
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Term
| What stage of the somatic cell cycle is typically short? |
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Definition
| 1) Chromosome division phase (M-stage) |
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Term
| The M-phase is only ___________ ___________. |
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Definition
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Term
| What stages are often eliminated in rapidly diving cells? As a result, how short does the mitotic cell cycle become? |
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Definition
1) G1 and G2
2) Less than 1 hour |
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Term
| What 4 stages are recognized within the M-phase of the somatic cell cycle? |
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Definition
1) Prophase
2) Metaphase
3) Anaphase
4) Telophase |
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Term
| What cell cycle leads to the formation of gametes? |
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Definition
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Term
| The chromosome number is ___________ during the ___________ division of meiosis. |
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Definition
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Term
| What occurs during prophase I of meiosis? |
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Definition
1) Homologous chromosomes pair
2) Reciprocal recombinations take place |
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Term
| All genetic variability (different genotypes and phenotypes) is due to what factors? |
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Definition
| 1) Recombinations and chromosome sorting |
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Term
| Out of the ___________ chromosomes in humans, ___________ pairs (___________) are common to males and females. |
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Definition
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Term
What is unique about the 23rd chromosome in humans?
What is the chromosome for men? For women? |
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Definition
1) The 23rd pair is shaped completely different than the other 22, primarily because it is composed of the sex gametes.
2) In men, the 23rd homologous chromosome is composed of an X and Y chromosome
3) In woman, the 23rd chromosome is composed of 2 X chromosomes. |
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Term
| True or False: The mechanism of sex determination (XX = female; XY = male) is only found in humans. |
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Definition
| 1) FALSE: The mechanism of sex determination (XX = female; XY = male) is also found in other organisms |
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Term
| True or False: Human females make only one kind of gamete (22 autosomes + X-chromosome) while human males make two kinds of gametes (22 autosomes + X or 22 autosomes + Y) |
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Definition
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Term
| Which sex in humans is the heterogametic sex? What does this mean? |
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Definition
1) In humans, the male is the heterogametic sex.
2) Males are the heterogametic sex, which means they produce 2 kinds of gametes: either 22 autosomes + the X chromosome, or 22 autosomes + the Y chromosome. |
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Term
What is an example of an organism in which the female is the heterogametic sex?
What are the sex chromosomes called in this case? |
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Definition
1) Chickens
2) Males are ZZ and females are ZW |
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Term
| True or False: For genes located on the sex-chromosomes, reciprocal crosses do not have variety in the results. |
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Definition
| 1)FALSE: For genes located on the sex-chromosomes, reciprocal crosses CAN give DIFFERENT results. |
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Term
| What experiment revealed that reciprocal crosses can give different results? Who was the individual that performed the experiment? |
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Definition
| 1) The first case of reciprocal crosses giving different results was found in eye color in Drosophila and was performed by Thomas Morgan |
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Term
| The wild type eye color in Drosphila is ___________ and it is dominant over the mutant ___________ eye color. |
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Definition
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Term
| What were the two conclusions Morgan found from the Drosophilia experiment? |
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Definition
1) The gene for color was located on the X-chromosome
2) The Y-chromosome did no carry a gene for eye color |
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Term
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Definition
| 1) The failure of chromosomes to separate during meiosis I or II. |
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Term
| What are the results of disjunction occurring in the first meiotic division? In the second? |
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Definition
1) Disjunction of the 1st meiotic division results in 4 abnormal gametes; 2 with extra chromosomes and 2 with fewer than normal chromosomes
2) Disjunction of the 2nd meiotic division results in 2 normal and 2 abnormal gametes; one with extra an extra chromosome and one with less than normal chromosomes |
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Term
| When nondisjunction occurs in a diploid it is called ___________ ___________. |
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Definition
| 1) Primary nondisjunction |
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Term
What is primary nondisjunction?
What is the result of primary nondisjunction? |
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Definition
1) Primary nondisjunction is when nondisjunction occurs in a diploid
2) The result is an aneuploid, an organism with an abnormal chromosome complement, either missing or having extra chromosomes: for example, XXY or XO flies. |
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Term
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Definition
| An organism with an abnormal chromosome complement, either missing or having extra chromosomes such as XXY or XO in flies. |
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Term
When aneuploids undergo __________ (such as an XXY female fly) they usually make __________ kinds of gametes (X and XY; proper segregation of the two homologous X-chromosomes).
However, there is a possibility of abnormal segregation of the two x-chromosomes (resulting in __________ and __________ gametes), a process known as __________ __________. |
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Definition
1) Meiosis
2) Two
3) XX
4) Y
5) Secondary nondisjunction |
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Term
| What are three unique characteristics of sex-linked traits? |
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Definition
1) The recessive allele is visible primarily in males (because they carry only one allele, they are hemizygous). In the females, there are 2 alleles and for rare recessive mutations, the other allele is almost always wild type.
2) Affected males do not have affected sons (the sons inherit their X-chromosomes from the mother) The daughters are carriers for the disease.
3) The gene reappears in the grandsons of the affected males. Half the grandsons express the recessive disease gene. |
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Term
| What does it mean for an individual to be hemizygous? |
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Definition
| 1) An individual having only one of a given pair of genes |
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Term
| Why do males who possess sex-linked traits not have affected sons? |
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Definition
| 1) The sons inherit their X-chromosomes from their mother, so only daughters are carriers of the specific disease. |
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Term
| True or False: There are very few X-linked dominant traits. |
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Definition
| 1) TRUE (due to strong selective pressure on dominant traits) |
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Term
| Why are many X-linked dominant traits expressed by females? |
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Definition
| 1) X-linked dominant traits are often expressed in heterozygous females due to the presence of two X-chromosomes. |
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Term
| Genes which are Y-linked are __________. |
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Definition
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Term
| What are holandric genes? |
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Definition
| 1) Genes which are Y-linked (confined to males) |
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Term
| True or False: The X-chromosome has a much lower density of genes than the Y-chromosome. |
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Definition
| 1) FALSE: The Y-CHROMOSOME has a much lower density of genes than the X-chromosome. |
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Term
| True or False: Humans must have a Y-chromosome to be male. |
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Definition
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Term
What disease is marked by XO chromosomes?
What are phenotypic characteristics of the disease? |
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Definition
1) Turner's syndrome (human females are sterile) in which the genome only has 45 chromosomes (only one X)
2) Females with the syndrome often have a shorter stature, web-neck, underdeveloped breasts, and internal sexual organs. |
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Term
| What disease is marked by XXY chromosomes? |
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Definition
| 1) Klinefelter's syndrome in which a male has 47 chromosomes with underdeveloped testes |
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Term
| What occurs with the 48 chromosomes XXXY variation of Klinefelter's syndrome? The XXYY? XXX? |
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Definition
1) 48 XXXY = some breast development
2) 48 XXYY = subnormal intelligence
3) 48 XXX = almost normal, fertile, female with slightly reduced intelligence. |
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Term
| What is X-chromosome inactivation? How does it occur in woman? Is it passed to offspring? How? |
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Definition
1) In mammals, only one X-chromosome is left active (even in normal females which are XX). This inactive X is highly condensed and cytologically visible in the interphase nucleus and is known as a Barr body.
2) Inactivation occurs on the 16th day after fertilization; either of the X-chromosomes can be inactivated randomly.
3) Yes
4) All descendants of that cell have the same inactive X-chromosome; as a result, mammalian females are X-chromosome mosaics. When you have extra X-chromosomes (such as XXX or XXXX females), all but one are inactivated. |
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Term
__________ __________ __________ is a process that occurs in mammals in which only one __________ __________ is left active. The inactive __________ is highly condensed and cytologically visible in the interphase nucleus and is called the __________ __________.
Inactivation occurs on the __________ day after fertilization. |
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Definition
1) X-chromosome inactivation
2) X-chromosome
3) X
4) Barr body
5) 16th |
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Term
| What is the SRY gene? What is it's role in sex reversal? |
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Definition
1) The SRY (sex-determining region on Y) is a gene that when injected into a developing normal XX-embryo yields a male mouse.
2) XX-females have small part of the Y-chromosome translocated onto one of the X-chromosomes and the XY females have deletions in the Y-chromosome. Use of the SRY gene has the potentiality of altering a male to a female and vice-versa. |
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