MutationsUnit 4 Part 1
Central Dogma of Molecular Biology
Transcription/Translation Review DNA cannot leave the
nucleus. Through transcription
an mRNA copy of DNA is made. RNA Polymerase
unwinds and unzips the DNA.
RNA Polymerase adds RNA nucleotides one at a time until it reaches a stop point on the DNA.
Once it reaches the stop point the mRNA sequence is released into the cytoplasm.
Transcription/Translation Review After the mRNA
sequence is released into the cytoplasm it attaches to a Ribosome.
The ribosome travels down the mRNA strand looking for a start codon (AUG).
After it finds the start codon a tRNA molecule attaches to the mRNA codons by an Anti-codonand drops off a specified amino acid.
A.A.
A.A.
A.A.
Anti-codon
Mutations
What happens if a mistake is made during one of these processes? A mutation may
result. What is a mutation?
Changes in the nucleotide sequence of DNA.▪ May occur in
somatic . cells (Acquired - aren’t passed to offspring).
▪ May occur in gametes. (eggs & sperm) and be passed to offspring (inherited.)
What causes Mutations
Random mistakes in the reproductive process or the transcription /translation process.
Chemicals:
Radiation:
Types of Mutations
1. Chromosome Mutations Affects a large
of DNA 5 types▪ Deletion▪ Inversion▪ Insertion . ▪ Translocation▪ Non-disjunction
Types of Chromosomal Mutations
Deletion Due to subtraction. A piece of a
chromosome is lost.
Inversion Chromosome
segment breaks off & flips.
Segment reattaches.
Types of Chromosomal Mutations
Duplication When an entire
gene segment is copied.
Translocation When 2 non
homologous chromosomes cross over.
Types of Chromosomal Mutations
Nondisjunction Failure of
chromosomes to separate during meiosis.
Causes gamete to have too many or too few chromosomes.
Is the cause of many
genetic disorders. EX. Trisomy 21
Types of Mutations – Gene Mutations
2. Gene Mutations Include:▪ Point Mutations▪ Frameshift
Change in the N base sequence of a gene.
May only involve a single nucleotide.
May be due to copying errors, chemicals, viruses, etc.
Gene Mutations
Change in the nucleotide sequence of a gene.
May only involve a single nucleotide.
May be due to copying errors, chemicals , viruses, etc.
Gene Mutations
Point Mutation Change of a single
nucleotide. Includes the
deletion , insertion, or substitution of ONE nucleotide in a gene.▪ EX. Sickle Cell
Anemia
Gene Mutations
Frameshift Mutation Inserting or deleting
one or more nucleotides.
Changes the “ word(codon)” like changing a sentence.
Proteins built _change_.
KaryotypeUnit 4 Part 1
What is a Karotype?
A picture of the collection of chromosomes found in an individual’s cells.
Tells you the chromosome number of an organism . 46 in humans.
Tells you the sex of an organism: XX = Female XY =
Male Can indicate whether
or not a chromosomal abnormality is present.
Karyotype
MALE FEMALE
Chromosomal Abnormalities
MONOSOMY
the condition in which a diploid cell is missing a chromosome.
TRISOMY
the condition in which a diploid cell has an extra chromosome.
Types of Chromosomal Abnormalities
Down Syndrome Extra 21st
Chromosome. Symptoms:▪ Distinctive shaped
eyes▪ Cognitive heart
abnormalities▪ Simian folds▪ Below average
cognitive ability▪ Protruding tongue▪ Short limbs
Types of Chromosomal Abnormalities
Turner’s Symdrome 1 X chromosome
and no match. Symptoms▪ Short stature▪ Webbed neck▪ Broad chest▪ Non-functioning
ovaries▪ sterility
Types of Chromosomal Abnormalities
Klienfelter’s Syndrome 2 X chromosomes and 1 Y Most common
chromosomal abnormality.▪ Symptoms▪ Underdeveloped male sex characteristics.▪ Reduced fertility.▪ Slightly feminime characteristics.▪ Potential language impariment.