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BIOS1167 Lecture Notes - Lecture 13: Quantitative Trait Locus, Y Chromosome, Epistasis

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6 Sep 2018

School

University of Sydney

Department

Biomedical Science

Course

Professor

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Document Summary

Multiple genes affecting a single trait = polygenic inheritance. Effect of internal and external environment (eg. exposure to alcohol) Single gene affecting more than one trait. Interactions between the products of genes (epistasis) Genes may become activated/inactivated at certain temperatures. Primary sexual characteristics: male or female sex mechanisms. Phenotypic traits from genes on the x and y chromosomes. Eg. some traits more common in males or females - because allele being carried on the x chromosome (absence on y chromosome)

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Related Questions

Match the following definitions with the correct term. (We have not yet cover all of them in class, but you can find them in your reading.)

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B.

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A single mutation affects several traits.

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The frequency with which individuals of a given genotype manifest the mutant phenotype.

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A phenotypic trait whose expression depends on the additive effect of a number of genes.

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Expression of a gene is dependent on whether it has been inherited from the male or female parent.

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Phenotypic effects on the offspring produced by the maternal genome.

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Genetic information transmitted by chloroplasts or mitochondria.

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The degree in which a phenotype for a given trait is expressed.

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Determines whether two mutations are at the same locus or different loci.

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Genetic differences that are due to alterations of the DNA that do not included changes in base sequence.

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Characteristic determined by a gene on a sex chromosome.

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Characteristic encoded on an autosome that is more readily expressed in one sex.

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A gene at one locus that masks or suppresses the effect of a gene at a different locus.

A.

pleiotropy

B.

cytoplasmic inheritance

C.

epigenetics

D.

polygeneic inheritance

E.

imprinting

F.

sex-influenced trait

G.

sex-linked trait

H.

penetrance

I.

expressivity

J.

maternal effect

K.

complementation test

L.

epistasis

Biology lab homework

Dragon Genes

http://www.concord.org/stem-resources/modern-genetics

BLY 121L - Take HomeAssignment

Due: Start of class time âAt thestart of class next week

Answers MUST beâ¦

â¢ typed (no smaller than 11-pointfont)

â¢ complete sentences (i.e., grammaticallycorrect â AND spell check!)

â¢ THIS IS NOT AGROUP EFFORT â NO POINTS WILL BE AWARDED, IF YOUR PAPER ISSIMILAR IN CONTENT AND WORDING TO THAT OF YOURPEERâS.

Complete ALL4 modules:

1. Intro& Rules

2. Meiosis

3. Pedigree andGenes

4. The PlatesProblem

Complete and answer all of the questions fromeach module.

Introduction

Breed dragons to yield several offspring anddevelop a chart for all of the phenotypic characteristics youobserve.

â¢ Note the genotype and dominant/recessivecondition for each trait.

â¢ When you reach this section of theexercise, be sure to change the genotype for all traits to completethe chart.

Whatare the traits exhibited by yourdragons?

**YOUMUST TURN IN YOURCOMPLETED CHART AND IT MUST BE LEGIBLE!

Rules

Dominance and Recessive Traits

What isthe chromosome number(ânâ) for thedragons?

Which trait(s)exhibit incompletedominance?

What does it mean fora trait to be incompletely dominant?

Noallelic combination is described as being heterozygousrecessive. Why do you thinkthis is thecase?

Some Traits are Sex-linked

Which dragontrait(s)is/are sex-linked?

How dosex-linked traits differ from autosomal traits?

Color and Lethal Combinations

Describehow the inheritance ofcolor is different from that of horns and/orwings.

On whichchromosome is the lethal combination exhibited? What is the lethalcombination?

Meiosis

What is the phenotypeof your new dragon?

Whichtraits areinherited from the mother dragon? AND Which traits are inherited from the father dragon?

Wereany traits expressed by the offspring that differed from either or both of the parents? If so, whatwere they?

How does meiosisallow for variation inoffspring?

How doesfertilization allow for variation in offspring?

Pedigree and Genes

Now that you know how to breed dragons, let'stry some selective breeding in the pedigree view. Use the cross tool tobreed a new generation of dragons; breed two of thedragons from this new (F1) generation. Repeat thisat least8 times.

What do younotice about the dragons as you continue to breed more generations?

Use the chromosome tool to closelyexaminethe dragonsâ genes. If you had trouble answering the sex-linkedquestion above, now you can observe and compare the Xand Y chromosomesâ¦

Can you find any genesthat are different among the members of your F8generation?

How many generationsdo you have to breed until all the dragons are exactly thesame?

You arecreating an inbred strain of dragons in the final generation(s)of this process. Write a notedescribing your strain, and explain what is âspecialâ aboutall individuals in an inbred strain of organisms.

The Plates Problem

Try breedingsome offspring to see resultsof these crosses. Does thepattern of inheritance ofplates tell you anything useful?

Based on yourbreeding experiments, where might you expectto find the gene forplates (i.e., On whichchromosome might the gene be located?) Why do you think this iscorrect?

Dragons thatgrow plates usually do so quite late in their life, so dragons thathave a new baby don't know right away whether or not it will growplates. Which trait(s)exhibited by a baby might helpa mother dragon determine whether her baby will growup to have plates?

DragonGenes
Genotypes/Phenotypes

Trait	Phenotype	Genotype
Horns	Horns
	No Horns
Wings	Wings
	No Wings
Legs	4 Legs
	2 Legs
	No Legs
Tails	Fancy Tail
	Plain Tail
Fire-breathing	Fire-breathing Male
	Non-fire-breathing Male
	Fire-breathing Female
	Non-fire-breathingFemale
Color	Green Male
	Yellow Male
	Red Female
	Blue Female
	Brown Female
	Purple Female

___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).