Download Basic Genetics Notes

Basic Genetics Notes
Inheritance
• You get DNA from your
parents
• DNA is the instructions
for your body
• Get ½ of DNA from your
mom
• The other ½ of DNA
comes from your dad
Genes
• A stretch of DNA
that tells your body
how to be.
• You inherit your
genes from your
parents.
• Genes are located
on chromosomes
• You have 23 pairs of
chromosomes
Phenotype
• A trait or characteristic seen in an organism
– There can be several versions (phenotypes) for the
same trait
– Phenotypes are usually expressed in words
– Examples: brown eyes, blue eyes, green eyes
Genotype
• Represents the DNA that gives a trait
– Use letters to represent the gene
– Different letters are used for different genes.
H = Hitchhiker’s thumb
allele
h = no hitchhiker’s thumb
allele
Alleles
• Different versions of the same gene.
– You have 2 copies of the same gene
– One copy from Mom and one copy from Dad.
– Alleles can either be dominant or recessive
– You can get a dominant or a recessive from either
parent
Dominant Allele
• A version of a gene that will appear in the
phenotype (will rule over the other versions)
– Capital Letters are used for dominant alleles
– Example:
• Purple flower allele (R) is dominant over white
flower allele (r)
• So the genotype of
RR = purple flower
Rr = purple flower
Recessive Allele
• A version of a gene that will only appear in the
phenotype if both alleles are recessive
– Use lower case letters
– For a white flower to appear, the genotype must be
(rr)
Homozygous Genotype
• When both alleles are either dominant (HH) or
recessive (hh). “Homo-” means “the same”.
Heterozygous Genotype
• When one allele is dominant and the other is
recessive (Hh). “Hetero” means “different”.
Write the question.
Answer in your own words.
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What does DNA do?
Why do you have 2 alleles for every gene?
How are genotypes and phenotypes different?
What is a dominant allele?
What is a recessive allele?
How are homozygous and heterozygous
different?
When you are done, show me and I’ll give you the
activity for today.