heredity

heredity - Heredity Recap Genes control the characteristics...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
Heredity
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Genes control the characteristics of living organisms Genes are carried on the chromosomes Chromosomes are in pairs, one from each parent Genes are in pairs Genes controlling the same characteristics occupy identical positions on corresponding chromosomes Recap 2
Background image of page 2
The gene pairs control one characteristic But they do not always control it in the same way Of the gene pair which help determine coat colour in mice, one might try to produce black fur and its partner might try to produce brown fur The gene for black fur is dominant to the gene for brown fur Dominance 3
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The genes are represented by letters The gene for black fur is given the letter B The gene for brown fur is given the letter b BB bb The genes must have the same letter but the dominant gene is always in capitals Symbols 4
Background image of page 4
The genes of a corresponding pair are called alleles This means alternative forms of the same gene B and b are alleles of the gene for coat colour B is the dominant allele b is the recessive allele Alleles 5
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
A black male mouse ( BB ) is mated (crossed) with a female brown mouse ( bb ) In gamete production by meiosis, the alleles are separated Sperms will carry one copy of the B allele Ova will carry one copy of the b allele When the sperm fertilizes the ovum, the alleles B and b come together in the zygote F 1 6
Background image of page 6
B B B B b b b b B b meiosis meiosis fertilization All offspring will be black (Bb) sperm mother cell ovum mother cell zygote
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The offspring from this cross are called the F 1 (First Filial) generation They are all black because the allele for black coat colour is dominant to the allele for brown coat colour These Bb mice are called heterozygotes . Because the B and b alleles have different effects; producing either black or brown coat colour The mice are heterozygous for coat colour The BB mice are called homozygotes because the two alleles produce the same effect. Both alleles produce black coats. The bb mice are also homozygous for coat colour. Both alleles produce a brown coat colour The next slide shows what happens when the two heterozygotes are mated and produce young 8
Background image of page 8
B b B b B b B b B B B b B b b b BB Bb Bb bb sperm mother cell ovum mother cell meiosis Possible combinations Fertilization sperms ova zygotes F 2 9
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
A neater way of working out the possible combinations is to use a Punnett Square* b B B b Draw a grid Enter the alleles in the gametes Enter the possible combinations female gametes male gametes BB Bb Bb bb These are the F 2 generation Punnett square 10
Background image of page 10
The offspring are in the ratio of 3 black to 1 brown Although the BB and Bb mice look identical, the Bb mice will not breed true. When mated together there is a chance that 1 in 4 of their offspring will be brown This is only a chance because sperms and ova meet at random A
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/29/2011 for the course BIO 218 taught by Professor Young during the Fall '11 term at BYU.

Page1 / 41

heredity - Heredity Recap Genes control the characteristics...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online