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Inheritance and Genetics
BI30-GB1 Investigate the mechanisms and patterns of inheritance.
Indicators
• a. Discuss Gregor Mendel’s importance as the “father of genetics”. (STSE, K)
• b. Discuss the historical development of scientific understanding of Mendelian genetics,
including the importance of statistical analysis, probability and significance. (STSE, K)
• c. Distinguish among the mechanisms of inheritance (i.e., dominant and recessive alleles,
sex-linked traits, codominance, incomplete dominance and multiple alleles). (K)
• d. Determine an organism’s phenotype from its genotype, and where possible, its
genotype from its phenotype. (K)
• e. Construct Punnett squares using P1 genotypes (i.e., homozygous and heterozygous) to
determine genotypic and phenotypic frequencies for F1 and F2 generations. (S)
• f. Explore patterns of inheritance by interpreting pedigrees. (K, S)
• g. Explore the factors (e.g., gene flow, genetic drift and natural selection) which influence
the prevalence (i.e., expression and frequency) of genes and alleles within a population.
(K)
Gregor Mendel
• Who is he?
Gregor Mendel
• Who is he?
Mendel’s Process
Mendel’s Laws
• Law of segregation –
• Law of independent assortment –
• Law of dominance –
Mendel’s Laws
• Law of segregation - states that allele pairs separate or segregate during
gamete formation, and randomly unite at fertilization.
• Law of independent assortment - when two or more characteristics are
inherited, individual hereditary factors assort independently during
gamete production, giving different traits an equal opportunity of occurring
together.
• Law of dominance - one of the factors for a pair of inherited traits will
be dominant and the other recessive, unless both factors are recessive.
Probability and Statistical Analysis
• Overlap of math and science!
• Use math and likelihood of events to occur to make inferences about
organisms!
• Why might this not always be accurate?
Vocabulary
• Heterozygous = has a genotype composed of two different alleles.
• Homozygous = has a genotype composed of two of the same allele.
• Allele = a copy of coding for a particular trait or gene loci (one letter).
A = capital letter means dominant.
a = lower case letter means recessive.
Gene loci = location of coding for an organism’s genetics (DNA),
typically for a specific characteristic – however, some
phenotypes are coded by multiple loci.
• Genotype = combination of alleles an individual possesses.
• Phenotype = the visible expression of the genotype (the code means we
see ________).
Vocabulary
• Monohybrid Crosses (A monohybrid cross is a mating between two
individuals with different alleles at one genetic locus of interest.)
• Dihybrid Crosses (A dihybrid cross is a mating between two individuals
with different alleles at two genetic loci of interest.)
• Codominance –
• Sex-linked –
• Autosomes –
Vocabulary
• Monohybrid Crosses (A monohybrid cross is a mating between two
individuals with different alleles at one genetic locus of interest.)
• Dihybrid Crosses (A dihybrid cross is a mating between two
individuals with different alleles at two genetic loci of interest.)
• Codominance – when two alleles are both represented in a
phenotype.
• Sex-linked – chromosomes/genes that are located on X or Y
chromosome.
• Autosomes – non-sex-linked chromosomes.
Vocabulary
• Incomplete dominance –
• Multiple alleles –
• Polygenic inheritance -
Vocabulary
• Incomplete dominance – one trait isn’t
completely dominant over the other so you
get a mixed phenotype.
• Multiple alleles - we end up with
two alleles for every trait in our phenotype.
• Polygenic inheritance - occurs when one
characteristic is controlled by two or more
genes.
Importance
• Why is it important to know about inheritance?
• Why might knowing about dominant and recessive genes be
important when considering offspring?
• Performing a test cross and looking at offspring can help us determine
genotypes, how?
Pedigrees
• Pedigrees help us establish family trees and determine potential
phenotypes/genotypes of offspring.
• They are useful in identifying characteristics (good or bad) that children
hold and whether or not they may be genetically linked.
• Functions as a record of descent. Can be animal-breed specific, or
characteristic specific.
• Create one using hair colour including one side of your grandparents (ie.
Mom’s side), your parents (and their siblings)
Genes and Natural Selection
Explore the factors (e.g., gene flow, genetic drift and natural selection) which influence the
prevalence (i.e., expression and frequency) of genes and alleles within a population. (K)
• How does expression/frequency of alleles connect to natural
selection?
• How does genetic drift/gene flow connect?
Genes and Natural Selection
Explore the factors (e.g., gene flow, genetic drift and natural selection) which influence the
prevalence (i.e., expression and frequency) of genes and alleles within a population. (K)
• How does expression/frequency of alleles connect to natural
selection?
Favourable traits actually reproduce to get passed on in a population.
• How does genetic drift/gene flow connect?
Certain traits may insert themselves into the gene pool as part of the
options!
Redheads originated in Ireland! Now they are apart of our gene pool!
DNA and Chromosomes
• a. Describe the structure and organization of chromosomes, including supercoiling of DNA. (K)
• b. Investigate the importance of meiosis, including crossing-over and homologous chromosomes,
in creating genetic variation in gametes. (K)
• c. Explore chromosomal recombination and mutation and their implications on evolution by
natural selection. (K)
• d. Recognize various types of chromosomal abnormalities (e.g., deletion, insertion, nondisjunction, inversion and translocation) and how they may lead to chromosomal disorders within
a variety of plants and animals. (K)
• e. Represent organisms’ genomes using karyotypes. (K, S)
• f. Identify the haploid, diploid and polyploid conditions of organisms, including those conditions’
advantages and disadvantages. (K)
• g. Investigate applications of and limitations to gene mapping as it pertains to single-gene and
polygenic traits. (K, STSE)
DNA
• Build a DNA molecule activity.
• Each strand of DNA represents
a chromosome!
• Double-helix structure of DNA
supercoils (bends and winds in
many ways). This allows it to
condense into a very small
area.
Meiosis and Crossing Over
• What is meiosis?
• What are gametes?
• What is crossing over?
• What is non-disjunction?
Meiosis and Crossing Over
• What is meiosis?
Process of producing gametes! PMAT
• What are gametes?
Sex cells, haploid copies of our DNA (chromosomes)
transferred to sperm and egg cells.
• What is crossing over/recombination?
exchange of genetic material between homologous
chromosomes that results in recombinant chromosomes
during sexual reproduction.
• What is non-disjunction?
is the failure of homologous chromosomes or sister chromatids
to separate properly during cell division.
Karyotypes
• A karyotype is…
Karyotypes
• A karyotype is…
is a test to identify and evaluate
the size, shape, and number of
chromosomes in a sample of
body cells. Extra or missing
chromosomes, or abnormal
positions of chromosome pieces,
can cause problems with a
person's growth, development,
and body functions.
Genetic Transmission,
Expression and Storage
BI30-GB2 Investigate the storage, transmission, and expression of
genetic information at the chromosomal level.
BI30-GB3 Investigate the storage, transmission, and expression of
genetic information at the molecular level.
DNA
• DNA: deoxyribonucleic acid
• RNA: ribonucleic acid
• Composed of sugar, phosphate
and nitrogenous bases
• Four (five) different types of bases:
Thymine (Uracil for RNA),
Cytosine, Adenine, Guanine
Protein Synthesis
Vocab
• mRNA – messenger RNA (carries messages from nucleus)
• tRNA – transfer RNA (transfers amino acids to ribosome)
• rRNA – what ribosomes are mostly composed of – allows mRNA to
“fit” into it.
• Helicase – DNA-splitting enzyme
• DNA Polymerase – creates new DNA strands
• RNA Polymerase – creates RNA strands (like mRNA)
• Codon – three-nucleotide “code” for a particular amino acid.
Protein Synthesis
Replication  Transcription  Translation
Replication creates new copies of DNA
(perhaps to create a new cell). DNA Polymerase
reads and creates a new strand of DNA from an
unzipped DNA.
Transcription takes the information encoded in
DNA and encodes it into mRNA, which heads
out of the cell's nucleus and into the
cytoplasm. During translation, the mRNA
works with a ribosome and tRNA to synthesize
proteins.
Transcription
Transcription (creation of a “transcript” of DNA information)
Helicase (an enzyme), unzips the DNA inside the nucleus. DNA or RNA
Polymerase (other enzymes), binds to the DNA and “rides’ along it,
adding complementary base pairs until it reaches a stop. This
complementary new strand (for RNA Polymerase) is called mRNA or
messenger RNA and will exit the nucleus.
Remember: In RNA, Thymine = Uracil (Why? It’s less energy-intensive
than Thymine and makes it easier to create)
The mRNA then ventures from the nucleus to a ribosome in the cell’s
cytoplasm.
Translation
Translation (translation of mRNA into a combination of amino acids –
polypeptide chain):
The mRNA meets with a corresponding ribosome and awaits a tRNA (transfer
RNA – which transfers amino acids) to bond with/complement its code
(example: if the mRNA is CAG, the tRNA would be GUC). The code, or codon,
is a sequence of three DNA or RNA nucleotides that corresponds with a
specific amino acid or stop signal during protein synthesis. When bonded
with the mRNA in the ribosome, it allows a certain amino acid to be added to
the chain (the amino acid provided corresponds to the code).
Note: certain amino acids are considered “start codons” amino acids which
will start the amino acid, and some are called “stop codons” which will end
the amino acid chain.
(1) The DNA
transcribes its
message into
mRNA in the
nucleus
(2) mRNA
leaves the
nucleus
AU G
U A UCGAUCG U
DNA
mRNA
(8) The released amino
acids bond together to
form a protein.
nucleus
cytoplasm
AA1
(5) The tRNA found in
the cytoplasm finds its
specific amino acid
(AA)
AA1
AA2
AA2
(6) The tRNA carries the
amino acid over to the
ribosome
(7) The exposed codon of
the tRNA matches with
exposed bases of the
template, which causes
the tRNA to release the
amino acid. The free
tRNA returns to get
another amino acid
C A U
AU G
tRNA
AA4
(3) The mRNA moves to
find the appropriate
ribosome.
U A UCGAUCG U
A U C
G A C
AA1
AA3
AA2
A U G
(9) When the protein is
finished the mRNA and
ribosome disassemble so
that the ribosome is free
to be a protein synthesis
site again. The mRNA
may return to the nucleus
to be broken apart to
form more mRNA
ribosome
(4) The mRNA attaches
to the ribosome to
make a template
Chromosomal Abnormalities
• Deletion – we lose a base pair in the chromosome/DNA code (can happen
with mistakes in crossing over).
• Insertion - we gain a base pair in the chromosome/DNA code (can happen
with mistakes in crossing over).
• Point – change in a nucleotide at a specific point on the DNA (substitution).
• Frameshift – deletions that occur in an entire codon (can lead to the
creation of a wrong protein).
• Inversion – chromosome flips and is read in the opposite order.
• Translocation – non-homologues rearrange.
• Replication Slippage – when base units repeat, the polymerase can slip
past it or repeat by accident.
Genetic Expression
Why do certain genes activate at
different times?
• Environmental –
• Epigenetics –
• Homeobox –
Genetic Expression
• Environmental – certain things in the
environment can trigger certain
hormones to be created which can,
in turn, lead to the activation of
certain genes.
• Epigenetics – some genes, while
present on a chromosome may not
become activity, epigenetics seeks to
explain why
• Homeobox – sequences in genes
that typically code for growth or
activation of other genes, this
includes activation of genes for
certain anatomical developments
Importance of DNA
• a. Assess the importance of the structure of the DNA molecule to its capacity for storage, transmission, and expression of genetic
information. (K)
• NOT DOING! b. Discuss the contributions of various scientists (e.g., Chargaff, Franklin, Wilkins, Watson and Crick) to understanding
the structure of DNA. (K, STSE)
• c. Recognize various types of gene mutations (e.g., deletion, insertion, point and frameshift) and how they may lead to genetic
disorders. (K)
• d. Discuss the mechanisms of DNA proofreading and repair. (K)
• e. Assess the role of genetic mutation in the process of evolution. (K)
• f. Explain molecular genetic processes of DNA replication and protein synthesis, including the roles of DNA, mRNA, tRNA and rRNA.
(K)
• g. Model molecular genetic processes, including DNA replication, transcription and translation. (S)
• h. Investigate factors (e.g., environmental, epigenetic and homeobox [Hox]) that control genetic expression. (K)
• i. Model or simulate the techniques (e.g., agarose gel electrophoresis, polymerase chain reaction and DNA sequencing) used by
molecular geneticists. (S, K, A, STSE)
• j. Appraise the importance of understanding the structure of DNA to advances in various fields of biology. (A, K, STSE)
• k. Provide examples of current and emerging biotechnologies (e.g., recombinant DNA, genetic testing and screening, gene therapy,
stem cells and cloning). (K)