Review: DNA, Transcription & Translation. Structure DNA Code for proteins Double Stranded Helix Can...
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Transcript of Review: DNA, Transcription & Translation. Structure DNA Code for proteins Double Stranded Helix Can...
![Page 1: Review: DNA, Transcription & Translation. Structure DNA Code for proteins Double Stranded Helix Can NOT leave nucleus Made of Sugar (deoxyribose), Phosphate.](https://reader035.fdocuments.us/reader035/viewer/2022062804/5697bf771a28abf838c81705/html5/thumbnails/1.jpg)
Review:DNA, Transcription
& Translation
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StructureDNA
• Code for proteins• Double Stranded Helix• Can NOT leave nucleus• Made of Sugar
(deoxyribose), Phosphate & nitrogen base– Thymine– Adenine– Guanine– Cytosine
RNA• Copy of the code for
proteins• Transports code to
Ribosome• Single Stranded• Can leave nucleus• Made of Sugar (ribose),
Phosphate & nitrogen base– Uracil– Adenine– Guanine– Cytosine
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Replication• Occurs in nucleus.
• DNA makes a copy of itself.
T
A
C
G
G
C
A
T
G
C
C
G
T
A
C
G
G
C
A
T
G
C
C
G
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Transcription• Occurs in nucleus.
• DNA makes a mRNA copy of the code.
T
A
C
G
G
C
A
T
G
C
C
G
A
U
G
C
C
G
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Translation
• Occurs at Ribosome.
• mRNA binds with tRNA to build an amino acid chain or protein.
Every 3 letters represents one amino acid or
codon.
Example: GUU = Valine
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Summary
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Mutations
• Any change in DNA sequence is called a mutation.
• Mutations can be caused by errors in replication, transcription, cell division, or by external agents.
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Mutations
• Mutations can be harmful.– Sickle cell anemia
– Cystic fibrosis
•Mutations can be beneficial.–Phenotypic (physical) changes
–Flower color–Fur color
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Mutations
• Mutations can occur in both types of cells:– Body cells (muscle, skin, brain, bone etc)
– Gametes (Sex Cells – sperm or egg)
Skin Cells Sperm Cell & Egg Cell
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• Damage to a gene may impair the function of the cell.
• When that cell divides, the new cells also will have the same mutation.
• This can result in the cells growing and dividing rapidly, producing cancer.
Mutations in body cells• If a body cell’s DNA is changed, this mutation would
not be passed on to offspring.
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• Mutations that occur in the gametes or sex cells can be passed on to the offspring.
Mutations in Gametes
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• A point mutation is a change in a single base pair in DNA.
• A change in a single nitrogenous base can change the entire structure of a protein because a change in a single amino acid can affect the shape of the protein.
Types of Mutations
THE DOG BIT THE CAT.
THE DOG BIT THE CAR.
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• An example of a point mutation, is sickle-cell disease.
• Sickle-cell diseases cause the red blood cells to be deformed. The result is that they get stuck in the blood vessels, depriving tissues of oxygen, causing strokes, and blood clots.
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Types of Mutations
What would happen if a single nitrogenous base (letter) is deleted?
THE DOG BIT THE CAT.
THD OGB ITT HEC AT.
• A mutation in which a single base is added or deleted from DNA is called a frameshift mutation.
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• Sometimes during mitosis or meiosis chromosomes break and then rejoin incorrectly, or just a piece breaks off for good.
• Structural changes in chromosomes are called chromosomal mutations.
Chromosomal Alterations
Deletion- part is missing
Insertion- part breaks off and attaches in the wrong place
Inversion- part breaks off and attaches upside down
Translocation- breaks off and attaches to different chromosome
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• Occurs during meiosis, when chromosomes fail to separate properly.
Non-Disjunction
• Normal humans have:– 46 chromosomes
• 22 pair of Autosomes• 1 pair of Sex
chromosomes• Non-Disjunction:
– Too many chromosomes?
– Too few?– 47 or 45
chromosomes
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Normal karyotype
Is this a male or female?
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Down Syndrome• Also called Trisomy 21
– 3 chromosomes instead of 2
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• Some mutations seem to just happen, perhaps as a mistake in base pairing during DNA replication.
• These mutations are said to be spontaneous.
• However, many mutations are caused by factors in the environment, such as radiation, chemicals, and even high temperatures.
– Ex: Chernobyl explosion
Causes of Mutations
• Any agent that can cause a change in DNA is called a mutagen.