Chromosomal Mutations/Abnormalities Describe processes that can alter composition or number of...
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Chromosomal Mutations/Abnormalities Describe processes that can alter composition or number of chromosomes (i.e., crossing-over, nondisjunction, duplication,
Chromosomal Mutations/Abnormalities Describe processes that can
alter composition or number of chromosomes (i.e., crossing-over,
nondisjunction, duplication, translocation, deletion, insertion,
and inversion).
Slide 2
Chromosomal Mutations/Abnormalities A chromosomal mutation is a
change in the structure of a chromosome. There are processes that
can alter the composition or number of chromosomes in a cell(s).
These processes include: Crossing-over Nondisjunction Duplications
Translocations Deletions Insertions Inversions A karyotype, or
picture of all of the chromosomes found in a cell, can identify
changes to chromosome structure and number.
Slide 3
Crossing-Over Crossing-Over: The exchange (swapping) of
segments of homologous chromosomes. Crossingover causes gene
recombination, or a reassembling of the genes, which increases
genetic diversity.
Slide 4
Nondisjunction Nondisjunction Failure of sister chromatids to
separate during mitosis OR failure of homologous chromosomes to
separate during meiosis. Nondisjunction results in extra
chromosomes in some cells and missing chromosomes in other cells.
Examples of disorders caused by nondisjunction: Down Syndrome
Triple X Syndrome Klinefelters Syndrome Turners Syndrome Homologous
chromosomes do NOT separate Sister chromatids do NOT separate
Slide 5
Duplication Duplication: A part of a chromosome (genes) or is
copied resulting in EXTRA genetic information. A duplication
results in a chromosome with extra genes. Examine the pictures
below:
Slide 6
Translocation Translocation: The exchange of portions of
non-homologous chromosomes. (Remember crossing over is the exchange
of segments of homologous chromosomes...these processes are their
outcomes are very DIFFERENT!) During a translocation, genes from a
pair of autosomes exchanges with a different pair of autosomes.
(Genes from one of Pair 13 might swap with genes from one of Pair
2.)
Slide 7
Deletion Deletion: A segment of a chromosome (gene) is
removed.
Slide 8
Insertion Insertion: A segment of a chromosome (gene) is added.
(SEGMENTS ARE NOT SWAPPED BETWEEN CHROMOSOMES LIKE WE SEE IN A
TRANSLOCATION.)
Slide 9
Inversion Inversion: A segment of a chromosome is removed,
flipped over, and reinserted back into the chromosome.
Slide 10
Identify the chromosomal abnormalities!
Slide 11
Protein Synthesis: The process in which amino acids are
arranged through the process of transcription (DNA RNA) and
translation (RNA protein). BIO.B.2.2 Explain the process of protein
synthesis (ie., transcription, translation and protein
modification) BIO.B.2.3 Explain how genetic information is
expressed. BIO.B.2.4 Apply scientific thinking, processes, tools
and technologies in the study of genetics.
Slide 12
Protein Synthesis & Gene Expression DNA RNA Protein Traits
Genetic information flows in one direction from DNA to RNA to
proteins. This flow of genetic information determines what traits
you express. Three important processes occur in cells to allow this
flow of genetic information to occur: Step 1 : Replication Step 2:
Transcription Step 3: Translation replication transcription
translation
Slide 13
What is RNA and why is it needed? RNA stands for RiboNucleic
Acid. It is similar in structure to DNA, but has a few differences
that make it a necessary component for transcription and
translation to occur. DNARNA Number of strandsDouble (2)Single (1)
Type of SugarDeoxyriboseRibose LocationNucleusStarts in the nucleus
and exits Nitrogen BasesA, T, G, CA, U, G, C U = uracil Enzyme
UsedDNA PolymeraseRNA Polymerase TypesOnly 1Multiple types: mRNA =
messenger RNA tRNA = transfer RNA rRNA = ribosomal RNA
Slide 14
Types of RNA Messenger RNA (mRNA) carries the message that will
be translated to form a protein. (messenger) Transfer RNA (tRNA)
brings amino acids from the cytoplasm to a ribosome. (taxi)
Ribosomal RNA (rRNA) forms part of ribosomes where proteins are
made.
Slide 15
Transcription The process that copies the genetic code in DNA
onto a strand of mRNA. Steps: 1 st DNA unwinds and exposes segments
of DNA (genes). 2 nd The enzyme RNA Polymerase reads the DNA code
and helps assemble a mRNA molecule. 3 rd DNA rezips and stays in
the nucleus. mRNA leaves the nucleus and travels to the ribosome.
Follow the base pair rules, but remember that RNA does NOT have
thymine instead it has uracil! DNA sequence = A T G G C T A A T
mRNA sequence = U A C C G A U U A
Slide 16
Transcription
Slide 17
Translation Translation is the process in which the messenger
RNA (mRNA) molecule is translated into a strand of amino acids
(polypeptide chain = protein). Translation converts mRNA messages
into polypeptides or proteins. Translation occurs in ribosomes! A
codon is a sequence of three nucleotides of mRNA that codes for an
amino acid. codon for methionine (Met) codon for leucine (Leu)
Slide 18
Codon Chart The genetic code matches each RNA codon with its
amino acid or function.
Slide 19
An anticodon is a set of three nucleotides of tRNA that is
complementary to a mRNA codon. An anticodon is carried by a tRNA.
For translation to begin, tRNA binds to a start codon and signals
the ribosome to assemble. A complementary tRNA molecule binds to
the exposed codon, bringing its amino acid close to the first amino
acid. The ribosome helps form a polypeptide bond between the amino
acids.
Slide 20
Protein Synthesis
Slide 21
Organelle Roles in Protein Synthesis What role do the following
organelles play in forming a protein? Ribosomes site of protein
synthesis (assembly) Endoplasmic reticulum aids in the production,
processing and transportation of certain proteins Golgi apparatus
final processing and packaging of proteins before they leave a cell
Nucleus contains the instructions (DNA) for making a protein
Slide 22
How do mutations impact phenotype? Genetic mutations alter or
change the DNA sequence in a chromosome. The following are types of
gene mutations that may or MAY NOT affect the phenotype (physical
appearance) of an organism: Point mutation A single-base is copied
wrong and results in a different nucleotide sequence and POSSIBLY a
different amino acid sequence and protein. There are a number of
mutations that are considered point mutations. They include: Silent
mutations there is NO change in amino acid sequence or the type of
protein assembled. Missense mutations there IS a change in amino
acid sequence AND the type of protein assembled. Nonsense mutations
- there IS a change in amino acid sequence and it results in a STOP
codon stopping the formation of the protein. Frame-shift mutation
The addition or removal (insertion or deletion) of one or more
nucleotides which results in a different amino acid sequence and
therefore makes a different protein.
Slide 23
Point Mutation vs. Frameshift Mutation mutated base
Slide 24
What do we do with this knowledge?. Biotechnology & Genetic
Engineering! Biotechnology Any procedure or method that uses living
things to develop or modify products or processes for specific use.
The term is commonly associated with genetic engineering. Genetic
engineering has impacted the fields of medicine, forensics and
agriculture. The following are examples of biotechnology/genetic
engineering: Selective breeding The process of breeding organisms
that results in offspring with desired genetic traits. Gene
splicing A type of gene recombination in which the DNA is
intentionally broken and recombined using lab techniques. Cloning A
process in which DNA, a cell or an organism is copied from an
original source, therefore resulting in organisms which are There
are many types of cloning including DNA cloning, reproductive
cloning, therapeutic cloning (stem cell cloning). Genetically
modified organisms An organism whose genetic material has been
altered through some type of genetic engineering technology. Gene
therapy The intentional insertion, alteration, or deletion of genes
within an individuals cells and tissues for the purpose of treating
a disease.
Slide 25
Forensics Forensics: The science of tests and techniques used
during the investigation of crimes. DNA Fingerprinting DNA Gel
Electrophoresis
Slide 26
Introduction to Genetics BIO.B.1.2 Explain how genetic
information is inherited.
Slide 27
A closer look at chromosomes Chromosomes are located in the
nucleus of all eukaryotic cells. Chromosomes are made up of long
strands of DNA. A gene is a piece of DNA that directs a cell to
make a certain protein. The proteins made are responsible for
specific traits. Traits are distinguishing characteristics that are
inherited (such as eye color, hair color, etc...).
Slide 28
How do we know traits are inherited? Genetics is the study of
inheritance. Inheritance is the process in which genetic material
is passed from parents to their offspring. Gregor Mendel, the
Father of Genetics, laid the groundwork for genetics in the mid
1800s by studying pea plants and their traits. His experimentation
on pea plants led to the following conclusions: 1. Traits are
inherited as discrete units called genes. Each gene has a locus, or
a specific position on a pair of homologous chromosomes. 2.
Organisms inherit two copies of each gene, one from each parent. 3.
The two copies segregate during gamete formation because gametes
(eggs and sperm) only receive one copy of each gene. The last two
conclusions led to the Law of Segregation. Father of Genetics
Slide 29
Alleles An allele is any alternative form of a gene (variation
in nucleotide sequence) occurring at a specific location on a
chromosome. Alleles are often represented by letters. Each parent
donates one allele for every gene. Homozygous describes two alleles
that are the same at a specific locus. Heterozygous describes two
alleles that are different at a specific locus. RR Rr
Slide 30
Dominant vs. Recessive Alleles Dominant alleles are represented
by uppercase letters; recessive alleles by lowercase letters. A
dominant allele is expressed as a phenotype when at least one
allele is dominant. (Rr or RR = dominant; therefore the pea is
round). Both heterozygous (Rr) and homozygous (RR) genotypes
produce a dominant phenotype. A recessive allele is expressed as a
phenotype only when two copies are present. (rr = recessive;
therefore the pea is wrinkled). Most traits do not follow simple
dominant versus recessive patterns of inheritance (ex. Hair color,
skin color, eye color, height, etc).
Slide 31
Genes influence the development of traits! All of an organisms
genetic material is called the genome. A genotype refers to the
makeup of a specific set of genes. Examples: Tt, RR, bb A phenotype
is the physical expression or appearance of a trait. Examples:
tall, round, blue View this video entitled What are
phenotypes?
Slide 32
Punnett Squares The Punnett square is a grid system for
predicting all possible genotypes and phenotypes resulting from a
cross. The axes represent the possible gametes of each parent. The
boxes show the possible genotypes of the offspring. Punnett squares
display the probability that an event will occur.
Slide 33
Punnet Squares & Probability Probability is the likelihood
that something will occur. Probability predicts an average number
of occurrences, not an exact number of occurrences. Probability
=number of ways a specific event can occur number of total possible
outcomes Probability applies to random events such as meiosis and
fertilization.
Slide 34
Monohybrid Crosses Monohybrid crosses examine the inheritance
of only one specific trait. Mendels Law of Segregation is evident
in monohybrid crosses, and states that during gamete formation the
two copies of a gene will segregate or separate. In other words a
sperm or egg cell does NOT inherit both copies of moms genes AND
both copies of dads genes. Example: Trait = Fur ColorB = brown OR b
= white Bb x Bb BbBb
Slide 35
Dihybrid Cross Dihybrid crosses examine the inheritance of two
traits. Mendels Law of Independent Assortment is evident in
dihybrid crosses, and states that allele pairs separate
independently of each other during meiosis. In other words the
inheritance of one trait has no influence over the inheritance of a
different trait. Example:Trait = Fur color & Fur length
Slide 36
Sex-Linked Inheritance The chromosomes (autosomes vs. sex
chromosomes) on which genes are located can affect the expression
of traits. Two copies of each autosomal gene affect phenotype
(because autosomes are made of homologous chromosomes); however
this is not the case for sex-linked genes because they arent always
homologous.(genes on sex chromosomes). Mendels rules of inheritance
apply to autosomal genetic disorders. A heterozygote for a
recessive disorder is a carrier. A carrier is an individual that
carries one gene for a disorder and can pass it on to his or her
offspring, A carrier does NOT show signs or symptoms of the
disorder. Disorders caused by dominant alleles are uncommon.
(dominant)
Slide 37
Sex-Linked Inheritance Males and females can differ in
sex-linked traits. Genes on sex chromosomes are called sex-linked
genes. Y chromosome genes in mammals are responsible for male
characteristics. X chromosome genes in mammals affect many traits
since both males AND females have at least one X chromosome. All of
a males sex-linked genes are expressed because males do NOT have a
second copy of sex-linked genes (only one X and one Y). The gene
for color-blindness is sex-linked and located on the X chromosome.
B = Normal Vision b = Colorblind
Slide 38
Non-Mendelian Genetics Many factors can influence the
expression of traits. Non- Mendelian Genetics accounts for these
factors by studying the following: Incomplete Dominance
Co-dominance Multiple Alleles Polygenic Traits Epistatic Genes
Slide 39
Incomplete Dominance In incomplete dominance, neither allele is
completely dominant nor completely recessive. Heterozygous
phenotype is intermediate between the two homozygous phenotypes.
For example if a red rose is crossed with a white rose the F1
generation would all be pink roses.
Slide 40
Co-Dominance Co-dominant alleles will both be completely
expressed. Co-dominant alleles are neither dominant nor recessive.
Example: ABO blood types A blood type is co- dominant to B blood
type; therefore a third blood type AB is formed. Many genes have
more than two alleles and this concept is referred to as multiple
alleles.
Slide 41
Polygenic Traits Many genes may interact to produce one trait.
Polygenic traits are produced by two or more genes. Order of
dominance: brown > green > blue.
Slide 42
Epistatic Genes An epistatic gene can interfere with other
genes. The gene for albinism is an example of an epistatic
gene.
Slide 43
Pedigrees A pedigree is a chart for tracing genes within a
family. Pedigrees allow you to track genotypes and/or phenotypes
over multiple generations.