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Ch. 10 Mendel and Meiosis
I. Gregor Mendel’s Laws of Heredity
A. Why Mendel Succeeded - “The Father of Genetics”, used ___________ to understand heredity
a). _______________ – the passing on of characteristics from parents to offspring
b). _______________ – studies heredity
c). _______________ - characteristics that are inherited
1. Mendel chose his subject carefully – Mendel studied heredity in ______ plants. Garden
pea plants reproduce sexually, which means they have two distinct _______________
a). Gametes – ________ _______. Ex: sperm in males, and eggs
in females
b). _______________ – the transfer of male pollen grains to the
pistil of a flower
c). _______________ – the uniting of male and female gametes
Human Egg
Human Sperm
pollination
2. Mendel was a careful researcher. He only studied ____ variable at
a time.
B. Mendel’s Monohybrid Crosses – He crossed 6ft. tall plants with short
plants
Human Fertilization
(zygote)
a). _______ ________ – offspring with same parental traits
b). _______________ – offspring of parents that have different
forms of a trait
1. The first generation (“Parent”)
2. The second generation (“1st Filial”)
3. The third generation (“2nd filial”)
EX:
(P)
(P)
(F1)
(F2)
_______________ (hand fertilized)
_______________ (self fertilized)
_______________ (self fertilized)
4. The rule of unit factors – Mendel concluded that each trait has 2 factors that control it
a). _______________ – a genetic factor that controls a trait
R
R
b). _______________ – different versions of a gene for the
same trait
r
c). _______________ – the observed trait Ex: tongue
rolling
d). _______________ – the trait that disappeared Ex: nonr
roller
5. Mendel’s Laws:
a). The Law of
b). The Law of _______________ –
c). The Law of _______________
_______________ when 2 alleles are different, 1 allele
_______________ – gene pairs
– each pair of
can control the trait and 1 can be
segregate into gametes randomly and
alleles separates
hidden (ex: tall vs. short plants)
independently of each other
C. Phenotypes and Genotypes
a). _______________ – b). _______________
the way an organism
– the actual genetic
looks and behaves
makeup
Ex: tongue rolling
Ex: TT or Tt
Ex: non-roller
Ex: tt
c). _______________
– when 2 alleles for a
trait are the same
Ex: TT
Ex: tt
d). _______________ –
When 2 alleles for a trait
are different
Ex: Tt
D. Mendel’s Dihybrid Crosses – a test cross that looks at 2 traits at a time
1. The first generation cross –
2. The second generation E. Punntt Squares and Probability
(P) Round Yellow (RRYY) vs. Wrinkled Green (rryy)
(F1) 9:3:3:1 ratio
Genes on
10.2 Meiosis
chromosomes
A. Genes, Chromosomes, and Numbers – genes are lined up on
_________________________
1. Diploid and haploid cells
a). ___________ (2N) – a cell with 2 of each kind of
chromosome
Ex: human body cells (ex: cheek) ________________
b). _________ (N) – a cell with 1 of each kind
of chromosome
Ex: human sex cells (ex: eggs or sperm) N =23
Homologous
2. __________________ _____________________–
The 2 chromosomes of each pair in a diploid cell. Humans
have 23 pairs.
3. Why ________________? Sexual reproduction
ensures that no offspring is exactly like its parent. By sharing
genetic information, populations share favorable
characteristics that allow them to survive and reproduce
a). Meiosis – cell division that produces
_____ the number of chromosomes as the parent’s body cells.
b). ________________– male gametes
c). ________________– female gametes
Sexual
reproduction
d). ________________– a fertilized egg
e). _____________ ___ ________________
– produces and fuses haploid cells
B. The Phases of Meiosis
1. ________________– cells
replicate
chromosomes
2. ________________I – Tetrads (homologous chromosomes) condense
and pair-up closely
a). ____________ ____________– the
exchange of genetic information between nonsister chromatids
3. ________________I – homologous chromosomes line-up
in the middle of the cell
4. ______________ I - homologous chromosomes separate
chromosomes
5. ________________I – the cell divides into two diploid cells
6. The phases of Meiosis II – the cell divides again producing
_________ haploid gametes
prophase II
metaphase II
Anaphase II
Telophase II
C. Meiosis Provides for Genetic Variation
1. ____________ _____________– the recombination of genetic
information by crossing over or independent assortment of chromosomes
D. Mistakes in Meiosis
a). ________________– the failure of homologous chromosomes to separate during
meiosis
1. ________________ (2N + 1)- when
nondisjuction causes a extra chromosome in a
haploid cell
Ex: Down’s syndrome is trisomy of the 21st
pair. The individual has 47 chromosomes
2. ________________ (2N – 1) - when
nondisjunction causes a missing chromosome in a
haploid cell, the zygote usually dies
Ex: Turner’s syndrome (female with 1 X )
3. _____________________- when nondisjunction occurs in all the chromosome pairs
(deadly in animals)
Ex: some bananas, lilies, wheat