13.3 and 13.4 Flashcards by David Heiser Jr

changes to

the bases of DNA or RNA

mutations

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Change the DNA →

changes the mRNA

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Change the mRNA →

changes the protein

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Change protein →

changes trait

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mutations are usually

Usually are spontaneous and random

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Causes of mutations

Errors in DNA replication or transcription

Caused by environmental factors called mutagens

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ex of mutations

Ex UV radiation, x-rays, some chemicals (pollutants,

pesticides, tobacco products & smoke)

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Mutations can occur in:

somatic (body) and gametes (sex) cells

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(not passed to offspring but does

affect the organism)

somatic (body) cells

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(does not affect the organism

but will be passed onto offspring)

gametes AKA sex cells

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affect a single gene, nucleotide bases

changed

gene mutations

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produce changes in part of a

chromosome, the whole chromosome, or sets of chromosomes

Chromosomal mutations-

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affect only 1 gene, usually
happen during replication, can be passed on to every cell that
is produced from it

gene mutations

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2 types of gene mutations

point and frameshift

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Change or substituting 1 letter for
another in DNA

May or may not change the protein

point mutations

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point mutations are

substitutions

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frameshift mutations are

(insertions or

deletions)

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Adding or deleting 1 letter in DNA

These shift or change the “reading
frame” (the way the ribosome reads
the codons)

Causes big changes to protein
(proteins might not work)

frameshift mutations

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CAA and CAT code for same a.a., DOESN’T change the amino acid so does
not change protein, so neutral mutation

Changes only 1 amino acid and sometimes no effect if they still code
for same amino acid called

silent mutations

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Changes the codon to a STOP codon

Protein is shorter than usual and might not work

nonsense mutations

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Disorders Caused by Point

Nonsense Mutations

Cystic fibrosis

Muscular dystrophy

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Mutation that causes a lack of dystrophin, a
protein that keeps muscles intact

Leads to severe muscle weakness

Trouble walking, breathing, swallowing.

Often have a curved spine or difficulty in releasing
muscle tension

Live on average 40 or 50 years

Muscular dystrophy

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Chronic lung infections due to buildup of thick
mucus in lungs and pancreas

Cannot be around others with CF

Live on average 40 years

Cystic fibrosis

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(substitutions- point mutation) or (insertions and deletions
then called frameshift mutations)

Changes 1 amino acid because by changing 1 base in DNA which changes
the whole protein, if a frameshift mutation it is even worse because it
changes multiple amino acids

misense mutations

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Changes every amino acid after the mutation by changing the | “reading frame” of codons, so changes protein

Frameshift Mutations

1 base is added to DNA

addition

1 base is deleted from DNA

deletion

Disorders Caused by | Frameshift Missense Mutations

Sickle Cell Anemia- 1 base | Progeria- substitution

Single base change causes a change in hemoglobin shape Sickle cells struggle to move through blood vessels, leading to anemia (lack of oxygen), fatigue, frequent pain

sickle cell amenia

Very rare disorder where the protein (progerin) that slows aging gets easily destroyed. Cells age very quickly, leading to stiff joints, hair loss, and strokes. 13 year average life span Leads to fatal heart complications

progeria

Disorder Caused by | Insertion

Huntington’s Disease

Insertion of a gene multiple times Protein called Huntingtin carries molecules outside of the cell Disease causes destruction in the portion of the brain that controls movement, emotion and cognitive ability Currently no cure Generally affects those 30-50 years old (inherited)

Huntington's disease

Chromosomal Mutations-

deletion, duplication, Inversion-, translocation

1 section or gene of | chromosome deleted

deletion

1 section or gene of | chromosome is doubled

duplication

1 section or gene(s) breaks off and reattaches backwards

inversion

1 section or gene(s) breaks off and attaches to a NEW chromosome

translocation

chromosomal deletion ex

Example: Cri-du-chat (5p minus) – a piece of | chromosome 5

Inherited disease of the peripheral nerves(myelin sheaths) that control movement Causes slow loss of function and movement in arms/legs

Charcot-Marie Tooth Disease

Very rare disorder caused by a duplication of a region on the 22nd chromosome Heart and kidney defects Fused fingers & toes Some intellectual disabilities

cat eye syndrome

Disorders caused by Duplication

Charcot-Marie Tooth Disease | Cat Eye Syndrome

reverses the direction of parts of a chromosome.

chromosomal inversion

occurs when part of one chromosome breaks off and attaches to another.

chromosomal translocation

Example: acute myeloid leukemia (chromosomes 8 | and 21)

When chromosomes do not properly separate during meiosis (in anaphase) when gametes are formed

nondisjunction

Nondisjunction Can happen during 2 different times:

anaphase I, anaphase II

Anaphase 1

Homologous chromosomes do not | separate

Anaphase 2

Sister chromatids do not separate

Effects of Nondisjunction

If one chromosome is involved, one extra is called trisomy one less is monosomy

Have 3 copies of chromosome 21 Caused by non-disjunction of gametes, affecting embryonic development Delayed learning and physical growth Distinct facial features

Down Syndrome (Trisomy 21)

If nondisjunction involves a set of chromosomes:

The condition in which an organism has extra sets of | chromosomes is called polyploidy.

polyploidy ex

Triploid (3n) Tetraploid (4n) Polyploid (many sets)

often make use of “good” | mutations.

Plant and animal breeders

when a complete set of chromosomes fails to separate during meiosis, the ________ that result may produce triploid (3N) or tetraploid (4N) organisms.

gametes

are often larger and stronger than | diploid plants.

Polyploid plants

Important crop plants—including _______ and ______—have been produced this way.

bananas and limes

Polyploidy also occurs naturally in _____ plants, often | through spontaneous mutations.

citrus

Without mutations, organisms cannot evolve, because

mutations are | the source of genetic variability in a species.

Sickle cell disease is caused by a point mutation in one of the polypeptides found in

hemoglobin

the blood’s principal | oxygen-carrying protein.

hemoglobin

Among the symptoms of sickle cell disease are

anemia, severe pain, | frequent infections, and stunted growth.

mutations have helped many insects resist

chemical pesticides

Some mutations have enabled _________ to adapt to new | chemicals in the environment.

microorganisms

Flow of information from DNA to | protein to trait

gene expression

used to synthesize | proteins thus influencing traits

DNA sequences

In humans, some genes are always “turned on” for day to day function (Ex:

enzymes for cell respiration)

Genes that are “turned on” will be

transcribed and translocated into a protein

Controlling gene expression by turning genes “on” and “off” Controlled differently in prokaryotes and eukaryotes

gene regulation

Bacteria regulate gene expression by blocking transcription if protein not needed

prokaryotic regulation

group of genes regulated (turned on and off) together These genes usually have the same or similar functions

Operons-

Operons contain regulatory DNA sequences that allow regulatory proteins to turn the expression

up or down

regions allow RNA polymerase to bind to DNA, 1st right before gene

promoter

regions of DNA where repressor proteins can bind, right after the promoter, 2nd before the gene

operators

blocks RNA polymerase and turn operons “off”= no transcription so no mRNA made

repressors

turn operons “on” = binds to DNA for RNA polymerase to allow | transcription to occur so mRNA made

activators

Lac operon in E. coli turns on & off when bacteria needs to use

lactose

The lac operon is turned ___ when lactose is present.

Lactose binds to the repressor, allowing it to detach from the operon and for RNA polymerase can transcribe ____.

mRNA

is used to make enzymes needed to digest lactose (so gene is expressed).

mRNA

Most genes controlled individually ``` Different cells will express different sets of genes (even though they all contain the same DNA) → this makes cells specialize ``` Controlled by transcription factors (see next slide)

Eukaryotic Gene Regulation

Eukaryotic Gene Regulation includes the

TATA box

Proteins that form a binding site at TATA box to specific DNA sequences (promoter) to enhance or repress transcription by:

Help RNA polymerase bind to DNA promoter turn “on” OR Block access to promoter turn “off”

Most genes controlled by many

Most genes controlled by many | transcription factors

(Eukaryotes only)

Transcription Factors

Cells contain very small RNA sequences (called microRNA or miRNA) that aren’t mRNA, tRNA or rRNA These miRNA sequences become silencer complexes that bind to any mRNA that is complementary to the miRNA which blocks expression of that mRNA

RNA interference

A powerful way to study gene expression in the laboratory. May provide new ways to treat and perhaps cure diseases.

Using RNAi (RNA Interference) Technology

Make miRNA to synthetically turn off the expression of genes from

viruses and cancer cells

caused by a single autosomal dominant mutant gene. The gene produces a protein that causes brain abnormalities, which in turn interfere with coordination, speech, and mental abilities.

Huntington’s disease

helps cells undergo differentiation & become specialized in structure & function.

gene regulation

regulate organs that develop in specific parts of the body.

Homeotic genes-

similar 180-base DNA sequence found in homeotic genes.

Homeobox-

group of homeobox genes. located side by side in a single cluster tell the cells of the body how to differentiate as the body grows. Nearly all animals, from flies to mammals, share the same basic tools for building the different parts of the body.

Hox box

Common patterns of genetic control exist because

all these genes have | descended from the genes of common ancestors.

Environmental Influences on Gene Expression ex

Presence of lactose influences expression of lac gene in E. coli Himalayan rabbits develop dark spots in areas where heat is lost if reared in colder temps. Tadpoles speed up metamorphosis if they’re surrounded in a pond with many predators and little food

13.3 and 13.4 Flashcards

(94 cards)