MBLG2972 Lecture Notes - Lecture 6: Mendelian Inheritance, Centimorgan, Genetic Distance

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5 Jul 2018

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MBLG2072

Genetics and Genomics

Monica Zanuttini !

460381099

Lecture 6"Linkage and gene mapping

Why is linkage important? !

Determine the molecular properties of genes (e.g. breast cancer). Localise it to one

chromosomes & mapping it to speciﬁc position on chromosome. !

Identifying genes and biological processes underlying inherited traits.!

Functional genomics to discover why the gene causes the phenotype.!

Genetic tests for diseases and potential cures.!

A scaﬀold to inform the assembly of whole genome sequences. !

Can use this location to ﬁnd a potential cure for the disease. !

Linked genes: !

Genes which are linked together on a chromosomes (aka syntenic genes), so that their

alleles are often inherited together. However, if the genes are far apart on the same

chromosome, they can be unlinked. !

Estimation of the relative location of genetic markers, giving deﬁned points. Need a

combination of gene sequence with molecular and visible markers. !

Recombination: !

Recombination, or crossing over separates

alleles of linked genes.!

Recombination increases genetic variation by

producing new alleleic combinations.!

Occurs during prophase I of meiosis.

Crossing over occurs between chromatids of homologous chromosomes.$

Crossing over creates parental (P) and recombinant (R) gametes after segregation.!

Chiasmata are the sites of crossing over. !

Unlinked:"""""""!

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Document Summary

Determine the molecular properties of genes (e. g. breast cancer). Localise it to one chromosomes & mapping it to speci c position on chromosome. Identifying genes and biological processes underlying inherited traits. Functional genomics to discover why the gene causes the phenotype. A sca old to inform the assembly of whole genome sequences. Can use this location to nd a potential cure for the disease. Genes which are linked together on a chromosomes (aka syntenic genes), so that their alleles are often inherited together. However, if the genes are far apart on the same chromosome, they can be unlinked. Estimation of the relative location of genetic markers, giving de ned points. Need a combination of gene sequence with molecular and visible markers. Recombination, or crossing over separates alleles of linked genes. Recombination increases genetic variation by producing new alleleic combinations. Crossing over occurs between chromatids of homologous chromosomes. Crossing over creates parental (p) and recombinant (r) gametes after segregation.

Related Questions

Please show detailed work. Thanks in advance.

16. Syntenic genes can assort independently when

A) they are very close together on a chromosome.

B) they are located on different chromosomes.

C) crossing over occurs rarely between the genes.

D) they are far apart on a chromosome and crossing over occurs frequently between the genes.

E) they are far apart on a chromosome and crossing over occurs very rarely between the genes.

17. The alleles of linked genes tend to

A) segregate together more often than expected by random assortment

B) assort independently.

C) be mutated more often than unlinked genes.

D) experience a higher rate of crossing over.

E) assort independently and show a higher rate of crossing over.

18. If you know that the frequency of recombination between genes X and Y is 34% and between X and Z is 25%, can you predict the order of the three genes?

A) Yes; the order is X-Z-Y.

B) Yes; the order is X-Y-Z.

C) Yes; the order is Z-X-Y.

D) No; based on this data alone, the order could be Z-Y-X or X-Y-Z.

E) No; based on this data alone, the order could be X-Z-Y or Z-X-Y.

Question 19 - 20. You have performed the following dihybrid cross in Drosophila using the black body color (b) and vestigial wing (vg) mutations. The b+ (grey body) and vg+ (normal wing) are dominant wild type alleles. These genes are autosomal.

Female â b+ vg+/b vg Ã male â b vg/b vg

Progeny:

Phenotype # of Progeny

Grey body normal wing 965

Black body vestigial wing 944

Grey body vestigial wing 208

Black body normal wing 195

19. Assuming linkage between black and vestigial, the estimated recombination frequency would be:

0.17

0.09

0.82

1.00

0.50

20. What key test could you use to determine whether the observed offspring frequencies deviate from those expected by chance alone?

A) Pascal's triangle

B) The product rule

C) The Chi-square (Ï²) test

D) The law of random assortment

E) The sum rule

21. In a genome wide association study (GWAS) designed to map the gene(s) that control height you divide subjects into a group of 1000 who are all more than seven feet tall and a control group of 1000 people of average height. You find the following associations between two genetic markers and the height trait:

		Tall group	Control group
Marker 1	Allele A	20%	50%
	Allele T	80%	50%

Marker 2	Allele G	15%	15%
	Allele C	85%	85%

What is your best guess for which marker is more closely linked to a gene that influences height?

A) Marker 1

B) Marker 2

22. Two pure breeding parents produce red and white flowers. They are crossed and the F1 produces pink flowers. When the F1 are selfed to produce the F2, nine distinct classes of pigmentation are present among F2 individuals. What is your best guess of the minimum number of genes that underlie flower pigmentation in this species?

A. 2

B. 3

C. 4

D. 5

E. 6

23. In a quantitative genetic experiment you identify two genes that confer bands of color on the back of a fly. At each gene, a dominant allele causes one band of color. If flies that are heterozygous at both loci are crossed, what ratio of offspring do you expect in each phenotype (i.e., number of color bands) class? (answer options are given from lowest to highest band number)

A) 1:1:1:1:1

B) 1:2:2:2:1

C) 1:4:6:4:1

D) 4:4:4:4:4

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MBLG2972 Lecture Notes - Lecture 6: Mendelian Inheritance, Centimorgan, Genetic Distance

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