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Chapter 3- Genetics: The Science of Heredity Vocab and Study Guide
Section 3.1- Mendel’s Work
How are traits passed from parents to offspring?
1
Heredity- the passing of traits from parents to offspring.
Traits - different forms of a characteristic
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Chromosome - double rod of condensed chromatin, contains DNA.
Gene - a segment of DNA on a chromosome, that codes for a specific trait (instructions for making
of a specific protein).
DNA - genetic material that carries information about an organism.
2
Who was Gregor Mendel, and how did his investigations contribute to our understanding of genetics?
Identify traits in pea plants, and parent, F1, and F2 generations.
Laws of Inheritance
1. Inheritance of traits is determined by “factors” (genes).
2. Individuals inherit on factor from each parent.
3. Traits may not show up in an individual, but can still be passed to offspring. (recessive genes)
What is the difference between dominant and recessive alleles?
3
Allele- alternate forms of a gene that code for a single trait.
Dominant alleles - the allele whose trait always shows up when the allele is present (masks the
recessive)
Recessive alleles - the allele that is masked, when the dominant is present.
What is the difference between purebred organisms and hybrid organisms?
4
Purebred – an organism that has the same alleles for a trait.
Hybrid - an organism that has two different alleles for a trait.
5
Section 3.2- Probability and Heredity
How can we apply the rules of probability to solve genetics problems?
Punnett square - chart that shows all the possible combinations of alleles that can result from a genetic cross.
6
How are phenotypes related to genotypes?
Phenotype
Genotype
- outward physical appearance of an organism.
- organism’s genetic makeup. (combination of genes)
What is the difference between a homozygous allele pair and a heterozygous allele pair?
7
Homozygous - describes an organism with two alleles that are the same for a trait.
Heterozygous - describes an organism with two different alleles for a trait.
9
What is the difference between incomplete dominance, codominance, and dominant/recessive traits?
Incomplete dominance - A form of inheritance in which heterozygous alleles are both fully
expressed, resulting in a blended phenotype.
Codominance - A form of inheritance in which heterozygous alleles are equally displayed in the
phenotype.
Study Guide
Be prepared to:
Chapter 3 Section 1- Mendel’s Work
1. Using the diagram below, as an example of a breeding experiment:
A. Identify alleles of organisms. W= dominant allele w= recessive allele
B. Identify which traits are dominant or recessive.
Long wings or the “wildtype” is dominant, short wings are recessive
C. Identify whether the organisms involved are hybrid or purebred.
D. Label the different generations involved in the experiment. (P, F1, F2)
Purebred WW
Purebred ww
Explain Mendel’s Law of Inheritance using
examples from his experiments.
P
Hybrid Ww
1. Each trait is determined by “factors” (which
we now call genes)
Example: purple pea flower color is determined
by a dominant allele P.
Hybrid Ww
2. Offspring inherit one factor from each
parent.
Example: The purple flowers in the F1
generation inherited one dominant gene from
one parent and a recessive gene from the other
parent. Genotype Pp
F1
Purebred WW
Hybrid Ww
F2
Hybrid Ww
Purebred ww
3. Traits may not show up in the offspring but
can be passed to the next generation.
Example: F2 generation white flower inherited
both recessive alleles from the hybrid parents.
Chapter 3 Section 2 - Probability and Heredity (use separate Bikini Bottoms Review sheet)
1. Identify homozygous and heterozygous allele combinations homozygous PP, DD heterozygous Pp, Dd
2. Define and give examples of genotype and phenotype. genotype Pp= phenotype purple flower in pea plant
3. Given a word problem:
A. Identify genotypes from phenotypes.
B. Complete a Punnett square.
C. Identify the probability (% chance) of a given offsprings’ genotype and phenotypes.
Complete the problems on the separate review sheet for dominant/recessive, incomplete dominance, and
codominance allele combinations.
Bikini bottoms
review sheet