BIOL1102 Lecture Notes - Lecture 19: Triple X Syndrome, Xyy Syndrome, Y Chromosome

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pearcrab619

7 Jun 2018

School

Flinders University

Department

BIOD Biodiversity and Conservation

Course

BIOL1102

Professor

Karen Burke da Silva

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Chromosome nondisjunction:

- When the chromosomes do not segregate properly during mitosis or meiosis

- In humans, since most such embryos are non-viable, one might expect that these

errors would be extremely rare

- But identified in at least 5% of all pregnancies, making it the leading known cause of

foetal loss

- Only a small proportion foetuses survive to term but are cause of mental impairment

and developmental disabilities

At what point in the cell cycle could this problem occur?

1. Meiosis I

2. Meiosis II

3. At either stage 

Remember: the first cell division (meiosis I separates homologous chromosomes; the

second (meiosis II) segregates the sister chromatids of each homologue

Meiotic nondisjunction:

Other forms:

- Monosomy:

o A condition in which one chromosome is missing, abbreviated as 2n-1

- Trisomy:

o Has one extra chromosome 2n+1

- Monosomies and trisomies usually result from nondisjunction during meiosis. They

are more common in meiosis I than meiosis II

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Document Summary

When the chromosomes do not segregate properly during mitosis or meiosis. In humans, since most such embryos are non-viable, one might expect that these errors would be extremely rare. But identified in at least 5% of all pregnancies, making it the leading known cause of foetal loss. Only a small proportion foetuses survive to term but are cause of mental impairment and developmental disabilities. At what point in the cell cycle could this problem occur: meiosis i, meiosis ii, at either stage . Remember: the first cell division (meiosis i separates homologous chromosomes; the second (meiosis ii) segregates the sister chromatids of each homologue. Monosomy: a condition in which one chromosome is missing, abbreviated as 2n-1. Trisomy: has one extra chromosome 2n+1. Monosomies and trisomies usually result from nondisjunction during meiosis. They are more common in meiosis i than meiosis ii. It cannot occur at meiosis ii in the paternal, but can be either of the maternal.

Related Questions

Please help im really lost on this..

What kinds of mistakes in meiosis could produce an individualwith chromosomal trisomy?

Meiois 1 only
Meiosis 2 only
Meiosis 1 and 2
Neither of these could produce chromosomal trisomies

What would be the effect of a mutationthat prevented the function of meiosis-specific cohesins inmeiosis?

a.Would egg production or function be affected? Pleaseexplain

b.Would sperm production orfunction be affected? Please explain.

c.Whatif the mutation made the cohesins too stable, so they could not bereleased properly when sister chromatids separate in meiosisII?

Use diagrams to run through the stepsin meiosis, but this time please make the following types oferrors. Summarize the effect on the meiotic products for eachsituation.

a.In Meiosis I, both sets of homologous chromosomes for themedium chromosome segregate to the same pole.

b.In Meiosis I, one set of sister chromatids (medium) separatesprematurely, so that each segregates to opposite poles.

c.In Meiosis II, a set of sisterchromatids (medium) separates prematurely and both segregate to thesame pole.

indigoeagle915

Nondisjuction is a cell division error in which either homologous chromosomes or sister chromatids fail to separate and thus do not migrate to opposite poles. It is responsible for conditions such as monosomy (one member of a chromosome pair is missing) and trisomy (three copies of a chromosome is present rather than two).

Nondisjunction can occur during the first or second meiotic division.

Part A- Jill is heterozygous for gene A and is going to have a child with Jack, who is homozygous recessive for gene A.

Which of the following offspring genotypes could result from fertilization of a normal haploid sperm with an egg that had undergone nondisjunction in meiosis I?
Check all that apply.

1)AAa

2)Aaa

3)aaa

4)Aa

5)aa

6)a

I put AAa, Aaa, Aa, but it was not correct

Part B-

Which of the following offspring genotypes could result from fertilization of a normal haploid sperm with an oocyte that had undergone nondisjunction in meiosis II?

Check all that apply.

1)AAa

2)Aaa

3)aaa

4)Aa

5)aa

6)a

Part E-

If Jack and Jill have a child with an aaa genotype, during which meiotic division, and in which parent, could nondisjunction have occurred?

Check all that apply.

1) Meiosis I in the mother

2 Meiosis II in the mother

3) Meiosis I in the father

4) Meiosis II in the father

The answer is not Meisis I in the mother

___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).

BIOL1102 Lecture Notes - Lecture 19: Triple X Syndrome, Xyy Syndrome, Y Chromosome

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