Download Genetics Guided Notes: ANSWER KEY Name

Genetics Guided Notes: ANSWER KEY
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DNA – Deoxyribonucleic Acid; an acid in the nucleus of a cell that codes and stores genetic information
Gene – a section of DNA on a chromosome that directs the making of a specific protein
Trait – an inherited characteristic
Ex: Eye color, hair color, height, etc.
Heredity – the passing of traits from parent to offspring
Alleles – the different forms a gene may have for a trait
Ex: For the trait of eye color, there are alleles for: brown, blue, green, hazel, etc.
Genetics – the study of how alleles affect generations of offspring
Gregor Mendel – “Father of Genetics”
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Studied pea plants
Two Types of Alleles
Dominant – the form of an allele that seems to dominate or mask another form of the same allele.
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Written as a CAPITAL letter Ex: A
Recessive – the form of an allele that appears least often in offspring
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Written as a lowercase letter Ex: a
Because chromosomes are paired, each individual carries two alleles for any given gene.
Three Possible Allele Pairs
Homozygous Dominant – when an individual has two dominant alleles for a gene Ex : AA
Homozygous Recessive – when an individual has two recessive alleles for a gene Ex: aa
Heterozygous – when an individual has both a dominant and a recessive allele for a gene
Ex: Aa
Let’s go with something simple like which hand you write with: left-handed or right-handed.
Which hand you use is determined by a gene in your DNA that tells your body what to do.
The DNA that you have in your body was passed to you from your parents – heredity – so your parents
determined for you (without knowing it) which hand you would use.
Your DNA is in the form of a duplicated chromosome, because of that each gene has two alleles for which
hand you use.
Now, in humans right-handed is much more common (Let’s take a poll to be sure), so we call it the dominant
allele.
Let’s assign a letter to this dominant allele: R
We write it capitalized because it is the dominant allele.
Left-handed is less common so we call it the recessive allele.
Let’s assign a letter to this recessive allele: r
We write it lowercase because it is the recessive allele.
Remember you can have three possible allele pairs
RR – homozygous dominant, you are right-handed
Rr – heterozygous, you are right-handed
rr – homozygous recessive, you are left-handed
It all just depends on which alleles are passed on to you from your parents - heredity
Genotype – the genetic makeup of an individual
Ex: RR, Rr, or rr
Phenotype – the physical trait displayed by an individual
Ex: Right Handed or Left Handed