BIOL239 Lecture Notes - Lecture 4: Amphiprioninae, Sex Change, Y Chromosome

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amethystdonkey419

14 May 2018

School

University of Waterloo

Department

Biology

Course

BIOL239

Professor

Christine Dupont

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Set 4: Chromosomes

●Chromosomal theory of inheritance:

oHereditary information is on genes, which are located on chromosomes

oEgg and sperm contribute equally to genetic endowment of offspring through

their nuclei

●Centromere – DNA sequence, on top of which sits a complex of proteins (kinetochore)

●Sex determination

oHumans – presence of Y chromosome = male (e.g. XO is female, but sterile)

oDrosophila



– sex is determined by the ratio of X chromosomes to autosomes

oSex is not determined by X and Y chromosomes in all species, e.g. in some

moths, fertile males are XO, females are XX

oIn other species, sex is determined by environmental factors, e.g.

▪ clown fish (biggest and most dominant as female, all others are male and

the 2nd largest is her mate; if the female dies the second biggest becomes

the male → able to switch sex)

▪in some reptiles (e.g. alligators), sex is determined by temperature of

incubation

chromosomes and reproduction

- Mitosis: nuclear division that results in 2 daughter cells each containing identical

numbers of chromosomes to the parent cell. ⇒ Clones

- Meiosis: nuclear division that results in each egg and sperm containing 1/2 the number of

chromosomes found in other cells (somatic). ⇒ Unique

Drosophila

- phenotypes

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Document Summary

Chromosomal theory of inheritance : hereditary information is on genes, which are located on chromosomes, egg and sperm contribute equally to genetic endowment of offspring through their nuclei. Centromere dna sequence, on top of which sits a complex of proteins (kinetochore) Mitosis: nuclear division that results in 2 daughter cells each containing identical numbers of chromosomes to the parent cell. Meiosis: nuclear division that results in each egg and sperm containing 1/2 the number of chromosomes found in other cells (somatic). Drosophila phenotypes female: much larger in size, larger and longer wings, clear cut abs. Male: smaller in size, abs jammed tgt? hook on y chromosomes. Diploid (2 n ), haploid ( n ); n = number of chromosomes in a normal gamete. Karyotype always uses metaphase chromosomes (densed, x shape) Metacentric centromere in middle of chromosome; acrocentric centromere near one end. Trisomy 18 - lethal before or shortly after birth; lots of abnormalities.

Related Questions

Which one of the following examples could serve as an example to illustrate what is meant by "norm of reaction"?AnswerIn some reptiles, sex-type is determined by the egg-incubation temperature. For some species, eggs with the same genotype developing at higher temperatures develop into a different sex type than eggs with that genotype developing at lower temperatures.In birds and some moths, males develop if embryos have two Z chromosomes and females develop if they have a Z and W chromosome.In ants and bees, diploid individuals are typically female while most males arise from unfertilized haploid eggs.In humans, XXY individuals are Klinefelter males.

lemonarmadillo607

___1. Nationally, the most common cause of Down Syndrome is
a. nondisjunction of Chromosome 21 during meiosis
b. translocation of Chromosome 21 onto another chromosome
c. inversion of a large section of Chromosome 21
d. deletion of the Down Syndrome gene
___2. In humans, sex is determined by
a. The presence or absence of the Y chromosome
b. The ratio of X chromosomes to sets of autosomes
c. The temperature during fetal development
d. Which parent is stronger at the time of conception
___3. A translocation is
a. a chromosomal abnormality in which a piece of one chromosome breaks off and attaches to a different chromosome
b. an abnormality in which the chromosomes are translocated out of the nucleus
c. a condition in which the chromosome has broken in two places and come back together with the middle segment backward
d. an abnormality in which there is an extra copy of one chromosome
___ 4. In snapdragons, a red-flowered plant crossed with a white-flowered plant produces all pink-flowered offspring. But crossing two pink-flowered plants produces red, pink, and white in a 1:2:1 ratio. This is a good example of
a. Incomplete dominance
b. Dominance of the red allele over the white allele
c. Lethal effects of the pink allele
d. Sex-linkage of the flower-color alleles
___ 5. If a person with type AB blood marries a person with Type O blood, what blood types are possible in their children? (Assume this trait is a single-gene trait, not complicated by interaction with other genes).
a. A, B, AB, or O
b. A or B only
c. AB or O only
d. AB only 2
___6. In what phase of meiosis are haploid nuclei first formed? a. Anaphase I b. Metaphase II c. Telophase II d. Metaphase I e. Telophase I
___7. What is the phenotype of a heterozygous tall pea plant? a. tall b. Tt c. TT d. tt e. dominant
___ 8. If genes A and B are far apart on a chromosome, and A and C are close together, which of the following observations is expected?
a. Crossing over will occur more often between A and C than between A and B
b. Crossing over will occur at equal frequencies between A and C, and between A and B
c. Crossing over will occur more often between A and B than between A and C
___9. Sometimes an organismâs genotype for one gene masks the effect of a different gene. This phenomenon is called
a. Dominance
b. Incomplete dominance
c. Co-dominance
d. Epistasis
e. Variable expressivity
___10. The dominant allele of a gene is
a. The one that is expressed most often in a population
b. The one that is expressed most often in any particular cross
c. The one that is expressed in an individual that has two different alleles
d. The one that is most healthy to have, that gives the greatest fitness
___11. In human cells, DNA replication occurs
a. In S phase of interphase
b. In G1 phase of interphase
c. In G2 phase of interphase
d. In prophase of mitosis
e. Whenever the cell needs to read the DNA to make proteins
___ 12. A process in which recipient cells take up genes from DNA molecules floating free in the surrounding medium is called
a. conjugation
b. specialized transduction
c. generalized transduction
d. transformation 3
___ 13. Most calico cats are female. However, a few rare males are observed. What is the genotype of a male calico cat?
a. X BX 0
b. X OY
c. X BY
d. X BYY
e. X BX OY
___ 14. A type of red-green color-blindness is a sex-linked (X-linked) recessive trait in humans. Can a woman have this type of color-blindness?
a. Yes, a woman could be color-blind if her mother and father were both heterozygous.
b. Yes, a woman could be color-blind but only if she has an abnormal number of sex chromosomes.
c. No, women can't show sex-linked traits because they lack a Y chromosome.
d. No, women can't show sex-linked traits because they have two X chromosomes.
e. Yes, a woman could be color-blind if her father was color-blind and her mother was a carrier (heterozygous).

BIOL239 Lecture Notes - Lecture 4: Amphiprioninae, Sex Change, Y Chromosome

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