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Why you Look and Act Like You Do
   
DNA rendering by ynse on Flickr


Genetics is the study of genes, and tries to explain what they are and how they work

  • Genes are how living organisms inherit features from their ancestors e.g children usually look like their parents because they have inherited their parents' genes.
  • Genetics tries to identify which features are inherited and explain how these features are passed from generation to generation.

 

 

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Genetic resources11 by CIAT International Center for Tropical Agriculture on Flickr


In genetics a feature of a living thing is called a "trait"

  • Traits are part of an organism's physical appearance e.g examples of traits are  a person's eye-color, height or weight.
  • Other sorts of traits are not easily seen and include blood types or resistance to diseases.
  • The way our genes and environment interact to produce a trait can be complicated e.g the chances of somebody dying of cancer or heart disease seems to depend on both their genes and their lifestyle.

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Some traits are inherited through our genes:

  • Tall and thin people tend to have tall and thin children.
  • Such traits which result due to inheritance alone are our genotypes.
  • Genotype is all the genes an organism carries.
  • Other traits come from interactions between our genes and the environment.
  • A  child might inherit the tendency to be tall, but if they are poorly nourished, they will still be short.
  • Such traits  are due to the combined action of inherited genes and environmental circumstances and are called phenotypes.
  • Phenotypes are our visible traits like hair color, eye color and how tall we are.

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DNA rendering by ynse on Flickr

Genes are made from a long molecule called DNA.

 

1. DNA is copied and inherited across generations so we have traits similar to our parents.

2. The order of these units carries genetic information, similar to how the order of letters on a page carries information.

3. This information is the instructions for constructing and operating a living organism.

4. Different copies of a gene do not always give exactly the same instructions

5. Each unique form of a single gene is called an allele.

6. As an example, one allele for the gene for hair color could instruct the body to produce a lot of pigment, producing black hair.

7.  A different allele of the same gene might give  instructions that fail to produce any pigment, giving white hair. 

8.  As a second example, one allele of the eye-color gene produces green eyes and another allele of the eye-color gene produces brown eyes.

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                                                      How Do I Get My Parents Traits?

  • Humans have two copies of each of their genes.
  • When people reproduce they make copies  of their genes and put them into eggs or sperm.
  • Only one copy of each type of gene is put in the egg or sperm.
  • When an egg joins with a sperm, this gives a child a complete set of genes, one from their mother and one from their father for every one of their genes.
  • The different alleles you get from your father and mother give you your characteristics.

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Why is my hair not red like my fathers?

  • The effects of this mixing depends on the types (the alleles) of the genes you get from your parents.
  • If the father has two copies for an allele for red hair, and the mother has two copies for brown hair, all their children will get the two alleles that give different instructions.
  • Each will get one for red hair and one for brown.
  • The hair color of these children depends on how these alleles work together.
  • If one allele overrides the instructions from another, it is called the dominant allele.
  • The allele that is overridden is called the recessive allele.
  • In the case of a daughter with alleles for both red and brown hair, brown is dominant and she ends up with brown hair.

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