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Science Chap 5 - Genetics/Punnett Squares Quiz 2/25

Terms in this set (24)

Genetics
scientific study of heredity or how traits are passed down from parent to offspring
heredity
the passing of traits from parent to offspring
Chromosomes
come in pairs- one from mom and one from dad
(In humans, there are 23 total pairs)
Each pair carries alleles that go together to form a special gene or trait. i.e. eye color
Trait
specific characteristics such as seed color or eye color
Allele
The different forms of a trait that make up a gene pair
dominant allele
an allele that dominates or covers up another allele ; represented by a capital letter
recessive allele
an allele that gets covered up or hidden by a dominant allele (physically it seems to disappear); represented by a lower case letter
purebred
another name for a gene with homozygous alleles; an organism with the same two alleles for a trait; 2 dominant(BB) or 2 recessive (bb) genes
hybrid
another name for s gene with heterozygous alleles; an offspring that gets 2 different alleles for a single trait Ex: (Bb) or (Tt)
genotype
genetic makeup i.e.: letters
phenotype
physical characteristics - what it looks like - the way an organism looks or behaves; Ex: Brown hair
homozygous
two alleles that are the same. Ex: (BB) or (bb)
Heterozygous
(hybrid) two alleles that are different (B,b)
Bb
hybrid or heterozygous - shows dominant trait
BB
homozygous dominant - shows dominant trait
bb
homozygous recessive - shows recessive trait
What is the difference between a dominant and recessive allele?
A dominant allele is always expressed or evident. it is in a homozygous (BB) or heterozygous (Bb) pair. A recessive allele is only expressed when in a homozygous pair(bb).
probability
the likelihood a particular event will occur
Punnett Square
used to predict and compare the genetic variations that will result from a cross
Describe how dominant and recessive alleles are represented in a Punnett square?
Dominant alleles are represented with an UPPERCASE letter (B, T).
Recessive alleles are represented with a LOWERCASE letter (b or t).
Explain the difference between genotype and phenotype.
Genotype is the combination of alleles an organism contains.Ex: TT or Tt
Phenotype is the expression of the alleles in an organism or how the organism looks or acts. Ex tall or short
Gregor Mendel, an Australian monk who lived in the 1800's is known as the father of genetics. Explain why.
He was the first person to explain the mechanics of heredity
If an organisnm expresses a recessive gene, can you tell the genotype? Explain.
Yes, because two copies of a recessive allele must be present for the recessive trait to be expressed or evident. You have to have a pair of alleles for blue eyes to have visible blue eyes.
Be able to create and interpret Punnett Squares.
Be able to create and interpret Punnett Squares.
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