RNA and Gene Expression How does DNA determine our traits? By - - PowerPoint PPT Presentation

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Sep 23, 2022 238 likes •606 views

RNA and Gene Expression How does DNA determine our traits? By directing the synthesis of proteins Proteins represent functional genes Molecular flow of information is: DNA RNA Protein Gene Expression 1. Transcription Genetic

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RNA and Gene Expression

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How does DNA determine our traits?

By directing the synthesis of proteins
Proteins represent functional genes
Molecular flow of information is:

DNA RNA Protein

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Gene Expression

1. Transcription – Genetic information is

transferred from DNA to mRNA

2. RNA Processing – enzyme-regulated

modifications to the mRNA transcript (eukaryotes only)

3. Translation – mRNA information is decoded

to synthesize proteins

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“Unpacking” DNA

Before a gene is

transcribed, the chromatin must relax and expose a gene – this is called “unpacking” the DNA

The process of

transforming condensed chromatin into a more relaxed structure is accomplished by histone acetylation

ANIMATION

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RNA (Ribonucleic acid)

A nucleic acid

composed of ribose sugars, phosphates, and nitrogenous bases

How does RNA

differ from DNA?

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DNA RNA

Double stranded
Deoxyribose sugar
Adenine, Cytosine,

Guanine, and Thymine

Located in nucleus only

(side note – mitochondria and chloroplasts also contain DNA)

Single stranded
Ribose sugar
Adenine, Cytosine,

Guanine and Uracil

Nucleus, cytoplasm, and

ribosomes

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What molecules are required for gene expression?

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Gene Expression Molecules

1. mRNA
2. tRNA
3. rRNA
4. amino acids
5. ribosomes

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mRNA (messenger)

linear RNA that transfers genetic information

from DNA to ribosomes

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tRNA (transfer)

RNA (~80 nucleotides in length) twisted in

hairpin shape

supplies the amino acids to ribosomes for

translation

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rRNA (ribosomal)

globular RNA that composes ribosomes, forms

the peptide bond between amino acids during protein synthesis

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Amino Acids

monomers of proteins
linked together to form proteins during

translation

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Ribosomes

site of translation (third step of gene

expression)

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Gene Expression Animation This animation will show you an

verview of gene expression

ANIMATION

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Eukaryotic Gene Structure

Promoter
Exon
Intron
Terminator

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Gene Expression

1. Transcription
2. RNA Processing (eukaryotes only)
3. Translation

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Transcription and RNA Processing

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Transcription

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Transcription – Virtual Cell HHMI Transcription

Transcription Animations

ANIMATIONS

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RNA Processing

Enzyme-mediated modifications to the mRNA

transcript

1. Addition of a GTP cap to 5’ end (protection,

bind to ribosome)

2. Addition of a poly-A tail to 3’ end (protection)
3. Excision (removal) of introns: non-coding

segments of DNA (RNA splicing)

mRNA then exits the nucleus

ANIMATION

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RNA Processing

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Translation (Gene to Protein)

Genetic information from a sequence of

nucleotides in a gene is used to produce a sequence of amino acids in a protein

Occurs on ribosomes in the cytoplasm

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Translation

Initiation
Elongation
Termination

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Translation Terminology

Codon
Start codon
Ribosome
Stop codon
Anti-codon
mRNA
tRNA
rRNA

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Translation- Virtual Cell

ANIMATION

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Genetic Code

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HHMI Translation Animation

Translation Animation

ANIMATION

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RNA interference (RNAi)

Regulates gene expression at the level of

mRNA transcription

Example of an RNAi molecule is microRNA

(miRNA) –Degrades the target mRNA OR –Blocks translation of the mRNA

ANIMATION

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Phenotypes Are Determined Through Protein Activities

Post translation protein modifications

determine the function of proteins: –Transport proteins –Catalytic proteins –Structural proteins