Transcript Semester I Final Review

Semester I Final Review
The SEMESTER IS OVA!!!!!!!
Part I.
Meiosis and Punnett Squares
Standards: Meiosis
 BI2.
Mutation and sexual reproduction lead to
genetic variation in a population. As a basis for
understanding this concept:
 BI2. a. Students know meiosis is an early step in
sexual reproduction in which the pairs of
chromosomes separate and segregate randomly
during cell division to produce gametes containing
one chromosome of each type.
 BI2. b. Students know only certain cells in a
multicellular organism undergo meiosis.
 BI2. c. Students know how random chromosome
segregation explains the probability that a particular
allele will be in a gamete.
Standard Explanations
• BI2. a. Meiosis produces sex cells,
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chromosomes pairs are separated randomly
during this process, producing gametes
containing one chromosome of each type
(haploid).
BI2. b. Only sex cells (gametes) are produced
meiosis.
BI 2.c.-Chromosomes segregate randomly
during meiosis.
Standards:Meiosis and Punnett
Squares
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BI3. A multicellular organism develops from a single
zygote, and its phenotype depends on its genotype, which
is established at fertilization. As a basis for understanding
this concept:
BI2. d. Students know new combinations of alleles may be
generated in a zygote through the fusion of male and female
gametes (fertilization).
BI2. e. Students know why approximately half of an individual’s
DNA sequence comes from each parent.
BI2. f. Students know the role of chromosomes in determining an
individual’s sex.
BI2. g. Students know how to predict possible combinations of
alleles in a zygote from the genetic makeup of the parents.
BI3. a. Students know how to predict the probable outcome of
phenotypes in a genetic cross from the genotypes of the parents
and mode of inheritance (autosomal or X-linked, dominant or
recessive).
BI3. b. Students know the genetic basis for Mendel’s laws of
segregation and independent assortment.
Standards Explanation-Meiosis and
Punnett Squares
• BI 2.d.-New combination of genes (alleles) are
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produced from fertilization.
BI 2.e.-Half of an organisms chromosomes come
from each parent because of Meiosis.
BI 2.f.-XX-female, XY-male
BI 2.g.,3.a.-Punnett Squares
BI 3.b.-Mendel’s Laws-chromosome pairs
separate, and genes for different traits are
inherited independently of each other.
What we’ve learned so far…
• Chromosomes contain genetic info
• We get ½ our genetic info from our mom
and ½ from our dad
• We don’t look exactly like our parents or
siblings. Why?
• Meiosis-formation of sex cells (sperm and
egg)
• Human body cells=46 chromosomes
Chromosomes
Meiosis Vocabulary
• Homologous chromosomes-
chromosomes that each have a
corresponding chromosome from the
opposite-sex parent
• Crossing Over – exchange of portions of
chromatids, genetic recombination
What are sex cells?
• Scientific name–gametes (sperm and egg)
• In humans, gametes have 23 chromosomes
(haploid=1 set)
• Half of 46
• Fertilized egg contains 23 chromosomes from
each parent (diploid= 2 sets)
What happens during meiosis?
• Two stages (Meiosis I & II)
• Meiosis 1-divides homologous chromosomes,
crossing over
• Meiosis 2-divides sister chromatids
• 1 diploid cell produces 4 genetically different
haploid cells
Meiosis
Mendel’s Principle of Dominance
• Some alleles (diff. forms of gene) are
dominant and some are recessive
• Organisms with dominant alleles will
always show that form of the trait (YY, Yy)
• Organisms with recessive alleles will only
show that form of the trait when there are
no dominant alleles present (yy)
Mendel’s Laws
• Law of Segregation: alleles that make up a gene
separate from each other, or segregate, during
the formation of gametes.
• Law of Independent Assortment: the way in
which alleles from different genes separate and
then recombine is unconnected to other genes.
Allele Combinations
• Homozygotes- two identical alleles for a
certain trait (YY,yy)
• Heterozygotes- two different alleles for
the same trait (Yy)
What are Punnett Squares?
• Punnett Squares are…
• a grid system for predicting all possible
genotypes resulting from a cross.
• The sides of the square represent the
possible gamete genotypes of each
parent.
• Shows all possible genotypes of offspring
What’s actually happening?
Part II.
Evolution
Big Idea: Evolution
• is the theory that life has changed on
Earth over long periods of time through a
process called natural selection, where
individuals with beneficial inherited traits
produce more offspring than other
individuals. This changes the frequency of
the alleles in the gene pool. There is a
broad range of evidence that supports
evolutionary theory such as fossils,
anatomical evidence, and genetic
evidence.
Standards:Evolution
• BI7.
The frequency of an allele in a gene pool of a
population depends on many factors and may be stable or
unstable over time. As a basis for understanding this
concept:
• BI7. a. Students know why natural selection acts on the phenotype
rather than the genotype of an organism.
• BI7. b. Students know why alleles that are lethal in a homozygous
individual may be carried in a heterozygote and thus maintained in
a gene pool.
• BI7. d. Students know variation within a species increases the
likelihood that at least some members of a species will survive
under changed environmental conditions.
Standards Breakdown:Evolution
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BI7. The frequency of an allele in a gene pool of a population depends on many
factors and may be stable or unstable over time. As a basis for understanding this
concept:
BI7. a. Students know why natural selection acts on the phenotype rather than the genotype of
an organism.
Means: NS acts on the physical or physiological traits of an individual.
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BI7. b. Students know why alleles that are lethal in a homozygous individual may be carried in a
heterozygote and thus maintained in a gene pool.
Means: Lethal copies of genes (for homozygotes-have two copies of the gene) can be carried in the
gene pool by heterozygotes.
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BI7. d. Students know variation within a species increases the likelihood that at least some
members of a species will survive under changed environmental conditions.
Means: The more genetic variation a species has the better chance they will have of surviving a
changing environment because atleast some individuals will have the characteristics needed to
survive.
Standards:Evolution
• BI8. Evolution is the result of genetic changes
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that occur in constantly changing environments.
As a basis for understanding this concept:
BI8. a. Students know how natural selection determines
the differential survival of groups of organisms.
BI8. b. Students know a great diversity of species
increases the chance that at least some organisms
survive major changes in the environment.
BI8. e. Students know how to analyze fossil evidence
with regard to biological diversity, episodic speciation,
and mass extinction.
Standard Summaries:Evolution
• BI8. Evolution is the result of genetic changes that occur in constantly
changing environments. As a basis for understanding this concept:
• BI8. a. Students know how natural selection determines the differential survival of
groups of organisms.
Means: Survival of the fittest and the struggle for existence.
• BI8. b. Students know a great diversity of species increases the chance that at least
some organisms survive major changes in the environment.
Means: The more variety of organisms there are in an environment the better the
chances are that some organisms will survive any major environmental changes.
• BI8. e. Students know how to analyze fossil evidence with regard to biological
diversity, episodic speciation, and mass extinction.
Means: Trend in fossil evidence show evolutionary patterns.
What is natural selection’s role in
evolution?
• Natural selection-mechanism by which
individuals that have inherited beneficial
adaptations produce more offspring on
average than do other individuals.
• These adaptations occur over many
generations in a population (descent
with modification)
How does natural selection drive
evolution?
• Struggle for Existence-individuals within a
species compete for common resources
• Survival of the Fittest- Individuals better
suited for their environment reproduce
more and have more offspring
What are adaptations?
• The inherited characteristics that increase
an organism chances of survival are called
adaptations
• Natural selection results in changes of the
inherited characteristics of a population