BLG 307 Study Guide - Midterm Guide: Allosome, Allele, Zygosity

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4 Aug 2015

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Homologous chromosomes- pair of chromosomes one from the father (sperm) and one from the mother (egg) that look similar and carry genes for the same traits. But do not necessarily bring about the same expression of those traits. Sex chromosomes- x and y, which determine genetic sex: male= xy, female=xx. 2 of the 46 chromosomes are sex chromosomes. The other 44 are the 22 pairs of autosomes that guide the expression of most other traits. E. g. for thumb, one allele may code for loose thumb ligament( double jointed), one allele might code for tight ligaments. When the 2 alleles controlling a trait are the same, a person is said to be homozygous for that trait. When the 2 alleles are different, the individual is heterozygous sometimes one allele masks or suppresses the expression of its partner dominant the allele that is masked is said to be recessive. Phenotype: the way that genotype is expressed in the body, physical trait.

Related Questions

The fruit fly Drosophila has 8 chromosomes (2n = 8). This includesone pair of sex chromosomes (XX in females and XY in males). Theother three pairs of chromosomes are autosomes. I give you a vialof flies with two dominant mutations: the first one Stubble, Sb,makes the bristles short and stubby (wild type bristles are longerand pointed; Sb+), whereas the other one, Serrate, Ser, makes theedge of the wing serrated (wild type wings have a smooth, notserrated margin Ser+). The genes encoding both these traits are onchromosome 3.

I give you a vial of flies that carry both these dominantmutations. Set up a cross to determine if the two mutations are incis (that means that the mutant alleles are on the same homolog) orif they are in trans. Write out the cross along with the possibleoutcomes. Consider one possibility at a time.

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27. Based on what you learned about various genetic conditions, which of the following individuals is never produced?

	A.	A woman homozygous affected with Duchenne
	B.	A woman homozygous affected with red-green color blindness
	C.	An XYY boy affected with Duchenne
	D.	A woman affected with red-green color blindness who has a normal father and a carrier mother
	E.	A homozygous individual for Dimples

28. Which of the following is NOT correct about sex influenced traits?

	A.	Males and females with the same genotypes may have different phenotypes.
	B.	They can be seen only in one of the sexes, and that is the sex in which, the pattern of inheritance of the trait is dominant.
	C.	A male can inherit the allele of these traits from either of his parents.
	D.	Regardless of the sex of the parent, alleles of these traits can be equally transmitted to sons and daughters
	E.	Their phenotypic expression depends on the sex hormones

___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).

BLG 307 Study Guide - Midterm Guide: Allosome, Allele, Zygosity

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