DNA & RNA Summary

DNA & RNA Summary

Heredity: Is the passing on of features from parents to offspring by means of genes.

Gene: Is a section of DNA that causes the production of a protein.

Gene expression: Is the way in which the genetic information in a gene is decoded in the cell and used to make protein.

Characteristics: Are traits or features that are inherited genetically.

Structure of DNA

DNA stands for deoxyribonucleic acid. DNA is a double stranded molecule made up of elongated chains of sub-units called nucleotides. DNA contains four chemicals called base pairs which are:

-Adenine (A)

-Thymine (T)

-Guanine (G)

-Cytosine (C)

A joins with T (2 hydrogen bonds) and G joins with C (3 hydrogen bonds).

Each nucleotide is made up of a phosphate, a sugar and a base.

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DNA Replication

-Different base pairs join together A-T and G-C

-The Double helix unwinds

-An Enzyme breaks the bonds between the base pairs.

-The two strands of the double helix separate

-The new copies of bases attach to the exposed complementary bases.

-The DNA molecule acts as mould or template for the new DNA that is formed.

-The new double strand rewinds to form a double helix.

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DNA profiling

-The DNA is released from the cells

-DNA is cut into fragments of different length.

-Fragments are separated according size.

Patterns produced by the fragments are compared.

Examples of DNA profiling are forensic scientists and Paternity Disputes.

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RNA Structure

RNA stands for ribonucleic acid. RNA is singled stranded. RNA consists of four chemical bases which are

-Adenine (A)

-Uracil (U)

-Guanine (G)

-Cytosine (C)

A joins with U instead of T and G joins with C

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Difference between DNA and RNA

-DNA contains the sugar deoxyribose and RNA contains the sugar Ribose

-DNA contains the bases A, t, G and C and RNA contains the base A, U, G and C

-DNA is a double helix strand and RNA is singled stranded.

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Protein synthesis:

Transcription

-The DNA unwinds and the two strands separate. Enzymes are involved in this process.

-RNA bases in the cytoplasm moves across the nuclear membrane.

-RNA bases will match up with the complementary bases.

-RNA enzyme polymerase causes RNA bases to join together.

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Translation

-mRNA moves from the nucleus to the cytoplasm.

-Ribosomes are made up of ribosomal RNA and protein

-mRNA strands form weak bonds

-In a ribosome will be the site of protein synthesis

-tRNA molecules attracted to the mRNA

-tRNA is complementary to mRNA

-A start codon begins the process of translation.

– tRNA’s attach to the mRNA two at a time. Carrying their precise amino acids to the ribosome.

– tRNA molecules leave the ribosome leaving their amino acids.

-tRNA molecules continue to bind with the mRNA until a stop codon is reached.

-The amino acid sequence of the new protein is now complete.

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