Biology 160, week 3
How many autosomal chromosomes are in human DNA?
22. Chromosomes 1-22 are numbered roughly in order of decreasing size.
What are DNAs nitrogenous base pair? How are the base pairs held together? Are there any exceptions to this?
A base pair is either A-T or C-G. They are held together by hydrogen bonding. A-T pairs have 2 bonds, C-G have 3. The exceptions to this are rare but caused by environmental effects or (far less often) random mistakes, resulting in what we call mutations.
What are mutations?
A change in the genetic information of a a cell; the ultimate source of genetic diversity.
What is a silent mutation?
A change with no effect (most common)
What type of chemical reaction takes place to join the protiens / amino acids together? What is formed?
A dehydration synthesis and a peptide bond. The end product is a polypeptide.
What is a gene, in relation to DNA?
A eukaryote's DNA is made up of genes. A gene is a unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses). Genes / DNA are found in nucleus, mitochondria and chloroplasts.
What are codons? Give an example.
A three-nucleotide sequence on the mRNA that specifies an amino acid addition, "start" signal or "stop" signal.
Which part of the nucleotide does the following: Phosphate binds with? Sugar binds with? Nitrogenous bases bind with?
Phosphate group binds to the 3' (three-prime) and 5' (five-prime) position of sugar. Sugar binds with all the other things. The 1 (prime?) position of sugar. Nitrogenous bases will always form the same pairs in DNA when they bind with each other.
Name the process used to make billions of copies of genetic material.
Polymerase chain reaction (PCR)
What do ribosomes make?
Polypeptides which fold into proteins.
Name three scientists who were instrumental in the discovery of DNA?
Rosalind Franklin, who took the first crystallographic picture of DNA; James Watson and Francis Crick discovered structure based on her work.
How do amino acids connect?
The carboxyl group of one lines up with the amino group of another.
Name the process by which proteins are made.
The entire process by which proteins are made is called gene expression.
How are the DNA nucleotides bonded?
They use covalent bonds - sharing electrons between molecules.
DON'T ASK: What happens to create mRNA from tRNA?
This is how the nucleus "cleans up" the mRNA.
What are anticodons?
Three-nucleotide sequences on tRNA that are complementary to one of the mRNA codons. Located on the opposite end of tRNA from the amino acid.
Name the process of RNA polymerase making a strand of mRNA from DNA.
Transcription
...How are the billions of copies of genetic material then separated by size?
electrophoresis
What carries amino acids to the ribosome?
tRNA
Which part of the tRNA binds to the mRNA's codon?
Anticodon
Describe how translation takes place:
At the ribosome, the "code" on the mRNA is converted into a series of amino acids that are bonded together to make the protein.
What builds daughter DNA / complementary DNA / new DNA?
DNA polymerase. It works in a 5' to 3' direction, but moves in a 3' to 5' direction, adding new nucleotides ONLY at the 3' end of the sugar.
What is DNA replication?
DNA replication is what allowed for the process of evolution to work. "Perfect copies" from generation to generation except for random mutations or mutations caused by environmental effects.
How many different types of amino acids are there?
Five
What are STRs used for?
Forensics; solving crimes. Cells are collected at crime scenes and DNA extracted; multiple regions are amplified using PCR and separated using gel electrophoresis. It is then possible to compare STR banding patterns in databases with those found at crime scenes.
What do genes code for? What does this mean?
Genes code for mRNA (messenger RNA). It means each gene is responsible for production of a single polypeptide.
Where do transcription and translation each take place?
In eukayotes, transcription in happens the nucleus and translation happens in the cytosol and rough ER.
Name the five types of nitrogenous base:
Adenine, Thymine, Cytosine, Guanine and Uracil.
Name the agent responsible for breaking the bonds between nucleotides.
An enzyme called helicase breaks apart the DNA strand at its origin, preparing for replication/division. The 'unzipping' process of making mRNA from DNA is called transcription. DNA polymerase also 'unzips' the DNA to prepare it for replication.
Why is "translation" so named?
Because there's a change in "language" from nucleotides to amino acids.
What is deoxyribose, and how is it similar/different to ribose?
Both are 5-carbon sugars. Deoxyribose is the sugar found in DNA. Ribose is deoxyribose with one more O (O-H bond), and is the sugar found in DNA.
What is a chromosome made of?
DNA, which is a threadlike structure, coiled tightly many times around proteins called histones, which support its structure.
DNA stands for? What is it?
Deoxyribonucleic acid. Each single strand of DNA is a chain of four types of nucleotides, however DNA usually exists as a double-stranded structure.
How long is a human's longest DNA molecule?
Each human cell contains 23 DNA molecules, each containing from 500 thousand to 2.5 million nucleotide pairs. DNA molecules of this size are 1.7 to 8.5 cm long when uncoiled, or about 5 cm on average.
Where does the mRNA strand go so protein synthesis can start?
It goes to the rough ER; it is looking for a ribosome.
What does a karyotype show you?
It is a description of all one's chromosomes. It is a test to identify and evaluate the size, shape, and number of chromosomes in a sample of body cells. Extra or missing chromosomes, or abnormal positions of chromosome pieces that cause mutations can be identified - these can lead to problems.
What is a wild type?
It's a mutation
What are DNA's monomers called? what are they comprised of?
Nucleotides. Nucleotides are comprised of: a sugar called deoxyribose; one of four nitrogenous bases, either A, T, G, C; a phosphate group.
Adenine and Guanine together are known as?
Purines
Thymine, Cytosine, and Uracil together are known as?
Pyrmidines
How is RNA different from DNA?
RNA differs from DNA in three important ways: (1) it consists of a single strand of nucleotides, (2) its nucleotides contain ribose sugar instead of deoxyribse sugar, and (3) uracil (U) is substituted for thymine (T) as one of the four nitrogenous bases.
What enzyme is needed for protein synthesis to take place?
RNA polymerase.
How is the mRNA strand different from the parental strand of DNA?
RNA uses Uracil in the place of Thymine and it has ribose instead of deoxyribose
What does RNA stand for?
Ribonucleic Acid
What are STRs?
Stands for Short Tandem Repeat. STRs are short stretches of repeated DNA sequences. Different people have different numbers of STR copies along their chromosomes.
To which end of the growing DNA molecule does DNA polymerase add a nucleotide?
The 3' (three-prime) end.
How are the nucleotides bonded to each other?
The nucleotides are joined to one another by covalent bonds between the sugar of one nucleotide and the phosphate of the next, which forms a sugar-phosphate backbone with a repeating patter of sugar-phoshpahte-sugar-phospahte.
In what part of the cell is mRNA made?
The nucleus
While DNA polymerase is making the new DNA, what is the original strand called?
The parental strand.
What are ribosomes attached to?
The rough endoplasmic reticulum (rough E.R.) or nothing; like prokatyotes, eukaryotes also have "free-floating" ribosomes in their cytosol.
What is produced from transcription and translation?
Transcription produces RNA under direction of DNA . Translation produces polypeptides under the direction of RNA.
What does tRNA mean? What does tRNA do?
Transport RNA molecules that temporarily carry a specific amino acid on one end are called tRNA. They carry the amino acids to ribosomes making polypeptides.
How many sex chromosomes are in human DNA?
Two; the sex-determining X and/or Y chromosomes.
Are tRNAs specific for amino acids?
Yes.