what is genetics? objectives: 1. explain the history of genetics. 2. explain how genetics works
Post on 22-Dec-2015
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What is Genetics?
Objectives: 1. Explain the history of genetics.2. Explain how genetics works.
Genetics is the study of heredity.
Heredity is the passing of traits from parent to offspring.
TraitsA trait is a characteristic that you receive from your parents. For example: brown hair, blue eyes
Alleles Different forms
of a gene.
Dominant alleles- traits that cover up or masks other traits
Recessive alleles- traits that are masked and seem to disappear
What controls our traits? Genes are found on our
chromosomes.
Genes are made up of DNA.
Human body cells have 23 PAIRS of chromosomes…our sex cells have only 23 (total). Why?
Gregor Mendel - Father of Genetics
Lived in 1800’s in Eastern Europe
Was taught about plants by Father
Became a monk Famous experiment with
plants. Died without ever
knowing his work would become famous
Dominant and Recessive Factors
Dominant traits appear to dominate or cover up other traits.
Recessive traits appear to disappear…but do they?
Alleles Homozygous
Two alleles for a trait that are exactly the same.
Example: TT or tt
Heterozygous Two alleles for a
trait that are different.
Written as Tt
Genotypes
The inherited combination of alleles
Represented by letters Ex. The letter P might stand for
purple flowers in peas
Phenotypes
Are physical traits that show as a result of a particular genotype. Examples
Red is the phenotype for red flowering plants
Brown hair Blue eyes Tall Short
Traits that are carried by all members of a species.
Example: The ability to walk upright in humans.
Traits that make the individual different from othersof the same species.
Example: color of eyes, hair color, body build
Incomplete DominanceCan you explain how colors in flowers, for example, are blended? (For example, red and white alleles make pink flowers)
When both alleles are expressed in offspring, the condition is called incomplete dominance…in other words, no allele is dominant.
Read pages 243. Draw within a Punnett Square Mendel’s experiments with red and white flowers.
Punnett Squares*A tool used to predict results in genetics.*Uses your knowledge of dominant and recessive alleles.
Punnett Squares
Shows genetic makeup or genotype of an organism.
A capital letter (G) stands for a dominant allele.
A small letter (g) stands for a recessive allele.
Every cell in body has 2 alleles for a trait.
Practice using Punnett Squares
Now let’s practice using Punnett squares!