Genetics and Inheritance Year 10 Biology

Part 2:

Modes of inheritance

From one generation

to the next!

2.Genes are passed on from one generation to the next!

You are a product of maternal and paternal chromosomes passed on from your parents!

Inheritance

3.Genes are passed on from one generation to the next!

The passing of characteristics from one generation to the nextThis double set of genetic instructions (one set from each

parent) makes up your genotype (your set of genes). The visible expression of the genotype as a particular trait or

feature is called the phenotype. The phenotype may also be influenced by your environment

Your Phenotype is influenced by environmental factors!

Phenotype Environmental influence• Weight• Aging

• Diet and exercise• Stress levels and stress management, chemical

use/ exposure, UV radiation

4.Genes are passed on from one generation to the next!

Your phenotype is determined by your genotypeDuring fertilisation, the zygote receives a pair of each set of

chromosomes, the paternal and maternal chromosomes.

Two forms of the same gene (one from mum one from dad) These alternate forms of a gene are called allelesAlleles can code for a dominant trait or a recessive trait

5.Genes are passed on from one generation to the next!

Alleles can code for a dominant trait or a recessive trait

Dominant alleles are shown in capitals

Recessive alleles are shown in lower case letters.

The recessive trait is hidden in the presence of the dominant trait

6.Genes are passed on from one generation to the next!

Your alleles can be Homozygous or Heterozygous

7.Genes are passed on from one generation to the next!

Homozygous = two of the same alleles Heterozygous = two different alleles

A genotype for a particular gene can be described as:

-Homozygous dominant-Homozygous recessive -Heterozygous

Your Genotype

8.Genes are passed on from one generation to the next!

A heterozygous genotype means you carry a recessive allele that may be passed on to the next generation.

The allele is recessive so doesn’t show up as a phenotype in the parents

But can show up as a phenotype in the offspring

9.Genes are passed on from one generation to the next!Explain

some unexpected phenotypes!

Degrees of Dominance

10.Genes are passed on from one generation to the next!

Complete DominanceThe expression of one trait is dominant over the other

Partial DominanceCo-dominance Heterozygote has the characterisitcs of both parents(e.g. human blood groups)

Incomplete DominanceHeterozygotes show a phenotype that is intermediate between the phenotypes of the homozygotes(e.g. flower colour of snap dragons)

Co-dominance11.Genes are passed on from one generation to the next!

Heterozygote has the characteristics of both parents(e.g. human blood groups)

Incomplete dominance 12.Genes are passed on from one generation to the next!

Heterozygotes show a phenotype that is intermediate between the phenotypes of the homozygotes.

(e.g. flower colour of snap dragons)

Suggest how red, white and pink flowered offspring can result from pink flowered parents

13.Genes are passed on from one generation to the next!

Degrees of Dominance

14.Genes are passed on from one generation to the next!

Complete DominanceThe expression of one trait is dominant over the other

Partial DominanceCo-dominance Heterozygote has the characterisitcs of both parents(e.g. human blood groups)

Incomplete DominanceHeterozygotes show a phenotype that is intermediate between the phenotypes of the homozygotes(e.g. flower colour of snap dragons)