Unit 10 Vocabulary Terms: https://quizlet.com/_ve5s6
Unit 10 Study Guide: https://quizlet.com/_1e9t7z
Unit 10: Basic Genetics CONCISE Notes
1.
Heredity – the passing of traits from parent to
offspring
a. Genetics
– the study of heredity (the study of the
passing of traits from parent to offspring)
b. Traits
– characteristics that are inherited
i.
Carried on the sex cells (gametes); each sex cell contributes half the normal number of chromosomes
ii.
Alleles – alternate forms of genes, found on the
chromosomes
1. All
organisms have two forms of an allele, one inherited from the mother and one
inherited from the father
2. Sexual
reproduction combines the two alleles forming a gene
a. Fertilization
– when the male gamete (sperm) meets and joins the female gamete (egg or ovum)
b. Genes
– the combination of the two alleles; factors that control traits – found on a section of DNA
i.
The
Chromosome Theory of Inheritance
c. Gregor Mendel – the father of genetics
i.
Important in understanding why offspring have
traits similar to their parents
ii.
The Principle of Dominance and Recessiveness
(Law of Dominance)
1. Dominant
trait – the trait that is observed in the offspring (covers up the recessive
trait)
a. The
dominant trait will always show up if the dominant allele is present
b. Represented
by a capital letter (T for tall stems, Y for yellow seeds)
c. TT
ot Tt result in the dominant trait appearing in the organism
2. Recessive
trait – the trait that seems to disappear, that is masked or covered by the
dominant trait
a. The
recessive trait will only show up if the organism inherits two recessive
alleles
b. Represented
by lower case letters (t for short stems, y for green seeds)
c. tt
will result in the recessive trait showing up in the organism
iii.
The Principle of Segregation (Law of
Segregation)
a. Alleles
separate during gamete production so that each gamete carries only one form of
the gene
b. Ex.
The allele for hybrid purple flowers (Ww) will separate and one gamete will get
W, the other gamete will get w
iv.
The Principle of Independent Assortment (Law of
Independent Assortment) (not always true)
a. Factors
for different characteristics are not connected; they are independent of each other
i.
Hair color and eye color do not necessarily
travel together
v.
Experimented with pea plants – they have traits
that occur in only two forms:
Gregor Mendel's Experiments:
1. First
he used purebred plants
a. Purebred
– always produces offspring with the same form of the trait as the parent (these
will be either homozygous dominant or homozygous recessive for the trait)
b. Hybrid
– offspring of parents that have different forms of a trait (these will be
heterozygous for the trait)
c. The
parent plants are called the P1 generation
i.
The first set of offspring are called the F1
generation (F for Filial – son)
ii.
The offspring of the F1 generation are called
F2, and so on
2. Monohybrid
Cross – crossing one trait between parent organisms (4 square)
a. Probability
– the likelihood that a particular trait will be inherited in an organism
i.
Represented as a percentage, usually: 0, 25, 50,
75, or 100%
ii.
Can be represented as a ratio: 1 in 2 or 1:1
iii.
Can be represented as a fraction: 1/4, 1/2, 2/4,
4/4…
iv.
Ex. Flipping a coin: a 1 in 2 chance: 50%, 1/2,
1:1 ratio
b. Laws
of Probability – predicts the likelihood of the traits in an organisms offspring,
not necessarily what actually occurs
i.
Each toss of the coin is separate from the last
toss; the same probability every time
Video: Mendel's Pea Plants
3. Punnett
Square – chart used to show all of the possible combinations of alleles from a
genetic cross; helps determine the probability an organism will inherit a
particular trait
a. Genotype
– the genetic makeup of an organism; the combination of alleles – TT or Tt
b. Phenotype
– the visible trait; the physical appearance – Tall
stems
c. Homozygous
(pure) – having the same alleles for the trait – TT or tt
d. Heterozygous
(hybrid) – having different alleles for the trait – Tt
Video: How to Complete a Monohybrid Cross:
Using a Punnett Square
i.
Determine the alleles for the parents
ii.
Put one set of parents on the top of the Punnett
square, the other on the left side
iii.
Multiply (cross) the alleles beside the square
with the alleles above the square
iv.
Determine the possible genotypes of the
offspring in fraction, percent, and ratio
v.
Determine the possible phenotypes of the
offspring in fraction, percent, and ratio
f.
Test Cross – used to determine the genotype of
an individual with a dominant phenotype
i.
Cross the unknown dominant (T?) with a known
homozygous recessive (tt)
ii.
If the offspring all have the dominant trait,
then the genotype if homozygous dominant (TT)
iii.
If some of the offspring have the recessive
trait, then the genotype is heterozygous (Tt)
Video: How to Use a Test Cross
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