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Chapter 10
Intro to Genetics
Chromosome # and sets
• Humans have 46 chromosomes
– 2 sets of 23
• Each parent gives ____________ chromsomes
• N = 1 chromosome set (23 in humans)
– 1N = Haploid (gametes)
– 2N = Diploid (all our other cells)
Homologous Chromosomes
• Same Length
• Same Centromere position
• Have genes that control the
same traits
• Get 1 from mom, 1 from dad
Review
• How many sets of chromosomes are
necessary for life?
• How many sets are necessary for human life?
• Do homologous chromosomes always code for
the exact same version of a trait?
Sex or no Sex?
• Asexual
– less energy, faster,
identical genetics
– Mitosis or Binary Fission
• Sexual
– more investment, more
genetic diversity
– Meiosis and Fertilization
Meiosis
• Like mitosis, but twice in a row
– Creates 4 – 1n cells instead of 2 – 2n cells
– Differences in Meiosis I
• Prophase I, homologues pair and crossing over occurs
• Metaphase I homologues line up together
• Anaphase I homologues separate, not chromatids
– Differences in Meiosis II
• There is no DNA replication beforehand
• Starts with 2 - 2n cells; after separating centromes
(chromatids) results in 4 – 1n cells
Meiosis
Importance of Meiosis
• Creates 4 genetically VARIED
haploid gametes
• Crossing over in prophase I causes
VARIATION
• Independent assortment during
metaphase leads to VARIATION
– Whether you get moms or dads
homologue for each of the 23 types of
chromosomes
• Random Fertilization = VARIATION
Crossing over
Genetics beginnings
• Heredity = passing traits btw generations
• Mendel’s story
– Monk, botanist, statistician, ninja
– Carefully bred pea plants
Terminology
• P = parental plants
• F1 = first offspring
• F2 = offspring of F1 etc…
• Gene = characteristic
• Allele = form of gene
• Dominant vs. Recessive
i.e. Height
i.e. Tall or short
Mendel’s work
Mendel’s Pea Traits
Genotype
• The alleles of an organism
– Homozygous dominant
PP
– Heterozygous
Pp
– Homozygous recessive
pp
Phenotype
• The expressed trait
– Dominant
Tall
• May be what genotypes?
– Recessive
Short
Mendel’s Law of Segregation
• Only 1 allele per gamete (randomly)
Mendel’s Law of Independent Assortment
• Each homologous pair separates randomly
– You don’t inherit different genes/chromosomes
together
– Being tall doesn’t affect if you are purple
Lets Breed (Cross)
Recombination
• New gene combinations
– Crossing Over and Independent Assortment
– Creates unique chromosomes vs. parents
• Variation from IA alone is 2N
– N = number of chromosomes in 1 set
– In humans is 2^23 =
Linkage
• Separate genes are inherited together if:
– they are on the same chromosome (no IA)
– Can they ever separate?
Polyploidy
• Def: Organism with 1+ extra chromosome sets
– i.e. 3n human (triploid)
– In animals: generally bad
– Makes some plants
more productive
13-1 Selective Breeding
• Breed only animals with desired trait
• Ex: Chihuahua, Dairy Cows
Saint Bernard
Rescue dog
Husky
Sled dog
German shepherd
Service dog
Hybridization
• Hybrids may:
– Be more disease-resistant
– Produce more offspring
– Grow faster
– Be expensive/time-consuming to make
Inbreeding
• Not what family reunions are meant for
• Amplifies gene frequency: good or bad
– Used for creating/maintaining new breeds
• Is inbreeding evil?
Test Crossing
• Discover genotype of
organism w/ dominant
phenotype
• Breed with homo rec.
– If any offspring are rec…
10.1 Formative Questions
Segments of DNA that control the production
of proteins are called _______.
A. chromatids
B. chromosomes
C. genes
D. traits
1.
2.
3.
4.
A
B
C
D
10.1 Formative Questions
What is the term for a pair of chromosomes that
have the same length, same centromere position,
and carry genes that control the same traits?
A. diploid
B. heterozygous
C. homozygous
D. homologous
1.
2.
3.
4.
A
B
C
D
10.1 Formative Questions
How does the number of chromosomes in gametes
compare with the number of chromosomes in body
cells?
A.
B.
C.
D.
Gametes have 1/4 the number of chromosomes.
Gametes have 1/2 the number of chromosomes.
1.
A
Gametes have the same number of chromosomes.
2.
B
Gametes have twice as many chromosomes.
3.
C
4.
D
10.1 Formative Questions
What type of organisms only reproduce
asexually?
A. bacteria
B. protists
C. plants
D. simple animals
1.
2.
3.
4.
A
B
C
D
10.2 Formative Questions
What is the name for different forms of
a single gene that are passed from
generation to generation?
A. alleles
B. genotypes
C. phenotypes
D. traits
1.
2.
3.
4.
A
B
C
D
Sexual Reproduction and Genetics
10.2 Formative Questions
Which pair of alleles is heterozygous?
A. RR
B. Rr
C. rr
D. yR
1.
2.
3.
4.
A
B
C
D
Sexual Reproduction and Genetics
10.2 Formative Questions
In rabbits, gray fur (G) is dominant to black
fur (g). If a heterozygous male is crossed with
a heterozygous female, what is the phenotypic
ratio of the possible offspring?
A. 1:1
B. 1:2:1
C. 2:1
D. 3:1
1.
2.
3.
4.
A
B
C
D
10.3 Formative Questions
Which explains how the shuffling of genes
during meiosis results in billions of possible
combinations?
A.
B.
C.
D.
crossing over
gene linkage
genetic recombination
independent segregation
1.
2.
3.
4.
A
B
C
D
10.3 Formative Questions
Two genes on the same chromosome
may become separated during meiosis.
A. true
B. false
1.
2.
A
B
10.3 Formative Questions
What is the term for an organism that has one
or more sets of extra chromosomes in its cells?
A. diploid
B. gamete
C. hybrid
D. polyploid
1.
2.
3.
4.
A
B
C
D
Sexual Reproduction and Genetics
Chapter Diagnostic Questions
Which symbol is used to represent the
number of chromosomes in a gamete?
A. #
B. x
C. r
D. n
1.
2.
3.
4.
A
B
C
D
Chapter Diagnostic Questions
Name the person known as the father of
genetics.
A. Felix Mendelssohn
B. Gregor Mendel
C. Dr. Reginald Punnett
D. Albert Einstein
1.
2.
3.
4.
A
B
C
D
Chapter Diagnostic Questions
Which term refers to the outward
expression of an allele pair?
A. gamete
B. hybrid
C. phenotype
D. genotype
1.
2.
3.
4.
A
B
C
D
Chapter Assessment Questions
How many chromosomes would a cell have
during metaphase I of meiosis if it has 12
chromosomes during interphase?
A. 6
B. 12
C. 24
D. 36
1.
2.
3.
4.
A
B
C
D
Chapter Assessment Questions
Which stage of meiosis
is illustrated?
A. prophase I
B. interphase
C. anaphase I
D. anaphase II
1.
2.
3.
4.
A
B
C
D
Chapter Assessment Questions
What is the next step for
the chromosomes
illustrated?
A. Chromosomes replicate.
B. Chromosomes move to
opposite poles.
C. Chromosomes uncoil
and form two nuclei.
D. Chromosomes line up
at the equator.
1.
2.
3.
4.
A
B
C
D
Standardized Test Practice
What is this process called?
A. fertilization
B. gamete formation
C. inheritance
D. reproduction
1.
2.
3.
4.
A
B
C
D
Standardized Test Practice
Before meiosis I, the sister chromatids
of this chromosome were identical.
What process caused a change in a
section of one chromatid?
A.
B.
C.
D.
DNA replication
crossing over
synapsis
telophase
1.
2.
3.
4.
A
B
C
D
Standardized Test Practice
At what stage is the
chromosome number
reduced from 2n to n?
A.
B.
C.
D.
prophase I
metaphase I
anaphase I
meiosis II
Standardized Test Practice
To which step in this
process does the law
of segregation apply?
A.
B.
C.
D.
grows into plant
gamete formation
fertilization
seed development
Standardized Test Practice
For human eye color, brown is dominant and
blue is recessive. If a husband is heterozygous
and his wife has blue eyes, what is the
probability that their child will have blue eyes?
A. 0
B. 1/4
C. 1/2
D. 1
1.
2.
3.
4.
A
B
C
D