Genes and DNA

Genes and DNA

Unit 4 Notes

Poll

How confident are you with remembering the nitrogen-base pairing system that is present in DNA?

• Totally confident

• Little fuzzy

• Need to hear it all again

Genes

A gene is a section of DNA molecule that contains the information to code for one specific protein.

Trait Production

The order of nitrogen bases (guianine, cytosine, adenine, and thymine) along a gene forms a genetic code that specifies what kind of trait will be produced.

RNA

RNA (ribonucleic acid) is responsible for being the "genetic messenger" that carries the genetic code from the DNA inside the nucleus into the cytoplasm.

mRNA

Messenger RNA copies the coded message from the DNA and carries the message to the ribosome in the cytoplasm.

tRNA

Transport RNA then carries amino acids to the ribosome and adds them to growing proteins.

Comparing DNA to RNA

• DNA has two strands

• DNA is composed of Deoxyribose sugar

• Nitrogen Bases include: Adenine, Guanine, Cytosine, Thymine

Comparing RNA to DNA

• RNA consist of one strand

• RNA is composed of ribose sugar

• Nitrogen Bases include: Adanine, Guanine, Cytosine, and Uracil (replaces Thymine)

Potential Issues

Since this genetic coding is such a delicate process, there are many steps in which the coding, replicating, and transfer process could be messed up. A mutation is any change in a gene or chromosome.

Kinds of Coding Mutations

• Substitution - switching one of the genes in the sequence with a different gene. You still have the same number of genes.

• Deletion - One of the genes in the sequence was deleted and now the strand is short one or more genes.

• Addition - An additional gene was inserted into the sequence, meaning now the strand has more genes than the initial DNA strand.

Example: If the original DNA sequence reads:

THE RED HAT

• Substitution would look like THE RED CAT

• Deletion would look like THE ED HAT

• Addition would look like THE READ HAT

Mutations

These mutations, along with the occasional change in the structure or number of chromosomes lead to what are called genetic disorders. Genetic disorders are inherited just like traits.

Multiple Choice

What is the first step in making a protein?

• An RNA copy is made of one side of a DNA segment.

• Amino acids are linked together.

• Bases on tRNA match up with bases on mRNA.

• mRNA is fed through the ribosome.

Multiple Choice

a change in the nucleotide-base sequence of a gene or DNA molecule that can affect the protein the DNA codes for

• mutation

• gene

• chromosome

• protein

• mutagen

Multiple Choice

A cell organelle where proteins are synthesized by messenger RNA and transfer RNA

• mutagen

• chromosome

• nucleotide

• ribosome

• gene

Multiple Choice

Which of the following genotypes is homozygous dominant?

• A
• Aa
• AA
• aa

Multiple Choice

Aa, DD, bB, yy are all examples of

• genotypes
• phenotypes

Multiple Choice

A gene determines a __________ such as eye or hair color.

• nucleus

• DNA

• chromosome

• Trait

Multiple Choice

What are sections of DNA called?

• DNA

• Genes

• Chromosomes

• Nucleus

Multiple Choice

Which of the following best describes the shape of a DNA molecule?

• double helix

• contains ribose

• made of amino acids

• contains Uracil

Multiple Choice

What does DNA stand for?

• Deoxyribonucleic acid

• Denitrogenous acid

• Deribonucleic acid

• Diribonucleic acid

Multiple Choice

The drawing shows the structure of what molecule?

• A DNA molecule
• A lipid molecule
• A carbohydrate molecule
• A protein molecule

Multiple Choice

Where in the cell is DNA found?

• Nucleus

• Cytoplasm

• Chloroplast

• Cell Membrane