2 24 Intro To Punnet Squares
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Transcript of 2 24 Intro To Punnet Squares
Launch
Correct the following false statements to make them true statements:
“We write the haploid number as 4N” “Somatic cells and sex cells both
undergo meiosis” “An example of a somatic cell is eggs” “An example of a germline cell is a brain
cell”
Mendelian Genetics
Mendelian Genetics
Mendelian Genetics is the study of how traits are passed down from parents to offspring
Father of Genetics
Gregor Mendel is considered to be the father of genetics
Gregor Mendel was an Austrian priest who made a lot of scientific discoveries about inheritance by studying peas and flowers.
Inheritance
Inheritance is the passing of traits from parents to offspring
Gene
A certain portion of DNA that codes for a specific protein Ex: Genes for hair color, eye color,
hormones, etc.
The rest of DNA is known as junk DNA.
Gene
Some traits are complex and require multiple genes Skin color
Allele
Alleles are different forms of one gene. Example:
The gene is hair color The alleles might be brown hair, blonde hair,
red hair, black hair, etc.
Genotype
The genotype is the way we describe the genetic make-up of an individual.
The genotype always consists of two letters: one for the allele from the mother, one for the allele from the father Rr, SS, dd
Phenotype
The phenotype is the physical appearance that is made as the result of an individual’s genotype.
The things we see!
Genotype
Alleles are either dominant or recessive.
When a dominant allele is present, you only see the dominant phenotype even if the recessive allele is also present.
Hh
Dominant
Dominant genes only require one allele to express the dominant phenotype.
Dominant alleles are represented in genotypes with a capital letter.
Examples: HH, Dd, SS, Tt,
Recessive
Recessive genes require both alleles to express the recessive phenotype.
Recessive alleles are represented in genotypes with a lower case letter.
Examples: hh, dd, ss, tt,
Heterozygous
Individuals are heterozygous for a gene when they receive a dominant allele from one parent and a recessive allele from another parent.
Rr, Ss, Tt, Uu
Think-Pair-Share
Why do individuals heterozygous for a gene always produce a dominant phenotype?
Homozygous
Individuals are homozygous when they receive the same allele from both parents Individuals are either homozygous
dominant or homozygous recessive
RR, rr, SS, ss
Exit Slip
1. __________ do mitosis, __________ do meiosis A. brains cells, heart cells B. eggs, sperm C. sperm, brain cells D. brain cells, eggs
2. If an individual is “Hh” for a trait1. Is this individual homozygous or heterzygous?2. Have a dominant or recessive trait?