Essay on Genetics and Recessive Allele

Submitted By Molly-Pavey
Words: 1072
Pages: 5

GCSE Science

Module B1 – You and your genes
What you should know

Name:

Science Group:

Teacher:

R.A.G. each of the statements to help focus your revision:
R = Red: I don’t know this A = Amber: I partly know this G = Green: I know this

B1.1 What are genes and how do they affect the way that organisms develop?
R.A.G.
I can recall that instructions to control how an organism develops and functions are found in the nucleus of its cells and are called genes

I can recall that genes are instructions for a cell that describe how to make proteins

I can recall that proteins may be structural (e.g. collagen) or functional (e.g. enzymes such as amylase)

I can recall that genes are sections of very long DNA molecules that make up chromosomes in the nuclei of cells

I understand that some characteristics are determined by genes (e.g. dimples), some are determined by environmental factors (e.g. scars), and some are determined by a combination of genes and the environment (e.g. weight)

I understand that many characteristics are determined by several genes working together (e.g. eye colour).

B1.2 Why can people look like their parents, brothers and sisters, but not be identical to them?
R.A.G.
I can recall that body cells contain pairs of chromosomes and that sex cells contain only one chromosome from each pair

I understand that chromosomes in a pair carry the same genes in the same place, but that there may be different versions of genes called alleles

I can recall that an individual usually has two alleles for each gene

I can recall that in an individual the two alleles of each gene can be the same (homozygous) or different (heterozygous)

I understand that during sexual reproduction, genes from both parents come together and produce variation in the offspring

I understand that offspring have some similarities to their parents because of the combination of maternal and paternal alleles in the fertilised egg

I understand that different offspring from the same parents can differ from each other because they inherit a different combination of maternal and paternal alleles

I understand that an allele can be dominant or recessive, and that:

a. an individual with one or both dominant alleles (in a pair of alleles) will show the associated dominant characteristic

b. an individual with one recessive allele (in a pair of alleles) will not show the associated recessive characteristic

c. an individual with both recessive alleles (in a pair of alleles) will show the associated recessive characteristic

B1.2 Why can people look like their parents, brothers and sisters, but not be identical to them? Continued
R.A.G.
I can recall that human males have XY sex chromosomes and females have XX sex chromosomes
.
I understand that the sex-determining gene on the Y chromosome triggers the development of testes, and that in the absence of a Y chromosome ovaries develop

I can use and interpret genetic diagrams (family trees and Punnett squares) showing: a) the inheritance of single gene characteristics with a dominant and recessive allele and b) the inheritance of sex chromosomes

I understand that the term genotype describes the genetic make-up of an organism (the combination of alleles), and the term phenotype describes the observable characteristics that the organism has.

B1.3 How can and should genetic information be used? How can we use our knowledge of genes to prevent disease?
R.A.G.
I understand that a small number of disorders are caused by faulty alleles of a single gene, including Huntington’s disease and cystic fibrosis
.
I can recall that disorders may be caused by dominant alleles (e.g. Huntington’s disease) or recessive alleles (e.g. cystic fibrosis)

I can recall the symptoms of Huntington’s disease – to include late onset, tremor, clumsiness, memory loss, inability to concentrate, mood changes

I can recall the symptoms of Cystic fibrosis – to include thick mucus,…