Inheritance of linked genes

Inheritance of linked genes
T4

Genetics
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BiologieMiddelbare schoolvwoLeerjaar 4

This lesson contains 14 slides, with interactive quizzes and text slides.

time-iconLesson duration is: 45 min

Items in this lesson

Inheritance of linked genes
T4

Genetics

Slide 1 - Slide

Learning Objectives
- You know the difference between independent and linked inheritance in dihybrid crosses
- You recognize whether a dihybrid cross inherits independently or in pairs
- You can work out linked, dihybrid crossings systematically.

Slide 2 - Slide

Types of crossings: what should I be able to do?
MONOHYBRID
regular
incomplete / co-dominant
multiple alleles
lethal factors
X-chromosomal

DIHYBRID
any combination of the two above types
independent
linked

Slide 3 - Slide

Linked inheritance

Both genes are on the SAME
chromosome
Independent inheritance

Both genes are on DIFFERENT
chromosomes

Slide 4 - Slide

Notation of Linked Inheritance
Because the alleles are literally 'linked' in linked inheritance, they are passed on to the offspring in fixed combinations. There is therefore less variation in gametogenesis (formation of sperm / egg cells).

It is very important that the alleles on the same chromosome are noted as such.
So use the following notation -->

Slide 5 - Slide

In fruit flies, the allele for gray body color (G) is dominant over the allele for black body color (g). The allele for normal wings (N) is dominant over that for wing stumps (n). Both genes are located on the same chromosome. A gray female with normal wings, homozygous for both traits, is crossed with a black male with wing stubs (vleugelstompjes).

Slide 6 - Slide

Give the genotypes of the female, male and of the F1 generation. Use the correct notation!
Also provide the corresponding Punnett square.

Slide 7 - Open question

The F1 is mutually crossed.
Give the phenotype ratio of the F2.

Slide 8 - Open question

A heterozygous male is crossed with a black female with wing stubs.
What genotypes can the male have? Use the correct allele notation!

Slide 9 - Open question

How can you determine which alleles of both genes are co-located on a chromosome (haplotype) if an individual is heterozygous for both linked genes?

Slide 10 - Open question

P. heterozygous male x black female with wing stumps.

F1. 48x gray flies with normal wings
51 x black flies with wing stubs.

What haplotypes did the P. generation male fly have? Support your answer with a Punnett square.

Slide 11 - Open question

What is the phenotype ratio in the F1. generation if in the 'father fly' the dominant G allele was linked to the recessive n allele (so has the other haplotypes)?

Substantiate your phenotype relationship by means of a crossing scheme.

Slide 12 - Open question

Learning Objectives
- You know the difference between independent and linked inheritance in dihybrid crosses
- You recognize whether a dihybrid cross inherits independently or in pairs
- You can work out linked, dihybrid crossings systematically.

Slide 13 - Slide

Work to be done
Biozone 153 (Inheritance of linked genes), Handout: Dihybrid crosses – 2 problems with linked alleles.  Biozone154 (Recombination and Dihybrid inheritance). Handout – Three problems illustrating no linkage, linkage and linkage with crossing over.  Assessment Questions Glencoe pg 320: Q 21-27 + 29  

Slide 14 - Slide