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.