B1- You And Your Genes (Detailed Summary)

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  • Created by: Maliha
  • Created on: 10-05-14 14:01

B1- YOU AND YOUR GENES

GENES, CHROMOSOMES AND DNA:

NUCLEUS-> CHROMOSOMEà DNAà GENE

Nucleus-

§  Most cells in the body have it and it contains genetic material

 

Chromosomes-

§  The genetic material in the nucleus is organised into chromosomes.

§  The human body cells have 23 pairs and the sex cell 23 individuals.

 

DNA Molecule-

§  Every chromosome has one long strand of DNA.

§  This gives the chromosome shape

 

Genes-

§  Short length of a chromosome.

§  They can come in different versions of the same genes which are called Alleles.

§  They control the development of characteristics e.g. eye colour etc. And the way an organism functions.

§  Each gene is a code for making a protein

§  Different versions of proteins means we end up with different characteristics

§  Structural proteins- skin hair blood etc. Collagen is a structural protein found in bones etc

§  Functional proteins- digestion and break down molecules. Amylase breaks down starch

 

Genotype & Phenotypes-

§  All of the genes it has

§  Characteristics the organism displays are called phenotypes

§  Come characteristics are controlled only by genes.

§  Other characteristics are caused by environment

§  Some characteristics can be controlled by both e.g. weight

 

VARIATION AND GENES

§  One chromosome comes from every parent

§  We have 23 pairs and 46 chromosomes

§  When the sperm fertilises the egg during reproduction, the fertilised egg cell will get 23 pairs of chromosomes

§  2 chromosomes in a pair are found in the same place and carry the same gene

§  Children will get some alleles from both parents

§  They will never be identical unless they are twins or clones

§  Every child will have a new combination of alleles

§  When people produce sperm or egg cells, their chromosomes separated go into different cells

§  Millions of different chromosome combinations

§  Brothers and sisters will look a bit alike but not entirely

 

INHERITENCE AND GENETIC DIAGRAMS

§  Combinations of alleles determines the phenotype and only one allele is shown

§  HOMOZYGOUS- two alleles the same for the particular gene

HETEROZYGOUS- two different alleles for the particular gene

§  DOMINANT- the more powerful allele which would always be shown against one recessive allele

RECESSIVE- The weaker allele that will only show when with another recessive alleles e.g. cystic fibrosis

 

GENETIC DIAGRAMS:

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQTIxAx_W3aYfUFtrr0V_MlosNGVGGNAMfl7GTo4iUL_HhBDpSY 

§  This diagram shows what happens when both parents are carriers of cystic fibrosis. The child has a 25% chance of becoming a sufferer and a 50% chance of becoming a carrier. However, there is only a 25% chance of being normal. By knowing how inheritance works, you can create family trees to interpret if the offspring will have a disease etc.

https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcTsHAWA2XR2IhxYTw4Lv7pyDQ1DEbUgg9dAyxSb85ZYKfeUrhP2

 

https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcTSHdEEsp60LKQETrrt6RMgdFujS3Z0_W2vQKSFMA0qoGrwNYkc 

 

 

 

 

 

 

 

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