Genetics Dna Exam Flashcards
What is the difference between DNA and RNA
DNA is the genetic material containing genes responsible for physical traits observed in organisms. DNA is replicated from existing DNA to produce new copies of the genome.
RNA is produced from DNA and a process called transcription RNA is the message used to make proteins called translation
What is the base unit of DNA?
A nucleotide
Each nucleotide consist of a sugar, a phosphate group, and a nitrogenous base
What are the three types of RNA and what are their roles?
mRNA – communicates the amino acid sequence for protein synthesis
TRNA – bring the correct amino acid to the growing polypeptide chain
rRNA-the side of protein synthesis in the ribosome
Purpose of DNA replication
For a cell to divide, it must replicate its DNA DNA is replicated from existing DNA to produce new copies of the genome
Where does DNA replication occur?
In the nucleus in eucaryotic cells, and in the nucleoid in prokaryotic cells
What does semi conservative mean?
Each resulting DNA molecule has one old and one new strength. This is called semi conservative replication because only the other strand is synthesized
Describe the steps of DNA replication, including lagging, and leading strand
Unwinding
Process begins at specific sites on double helix, called origin of replication first and enzyme, called helix splits the DNA down the middle we hydrogen bonds that hold the complementary nitrogen bases together are broken DNA now resembles a fork with two prongs(replication fork) one strand is called the leading strand, and the other is called the lagging strand as DNA strand separates it creates bubbles.
Base pairing
Two strands move apart, and each parent strand acts as a template or pattern to which free floating nucleotides in a cell can attach to replace the missing half RNA primer(primase) attaches to the beginning of one of the strands. Being the lagging strand RNA primer, attracts the free, floating, nucleotides nucleotides are attached. Their complementary bases replication along the DNA strand occurs in both directions original strand opens up as the new strand elongates all bubbles merge into two complete daughter DNA molecules DNA backbones run in opposite directions to one another each strand has a three primer end and a primer. three prime is attached to an OH group at one end and five prime is attached to a phosphate group at another end. DNA polymerase only add nucleotides to the three prime end therefore, a new strand only grows from five prime to three prime direction. One new strand can be made in one continuous piece by a DNA polymerase working toward the forking point of original DNA other new strand is made working out words from the fork, which causes short pieces at the fork opens which are called Okazaki fragments. an enzyme called DNA ligase ties pieces together into one single DNA strand. DNA polymerase also proofread, nucleotides and DNA repairs DNA some polymerases can correct errors made during replication when an incorrect base pair is recognized the polymerase versus its direction by one base pair. Then removes the incorrect base and replaces it with the correct one then continues with replication. This is called proofreading.
What are the parts of a DNA molecule?
Two twisted strands called the back bone made up of sugar and phosphate form the double helix structure. These hold the nitrogenous bases together that are in turn held together by hydrogen bonds.
What are the nucleotide pairings of DNA mRNA and tRNA
DNA pairings
Adenine – thymine
Cytosine – guanine
mRNA – complementary to DNA, except thymine is replaced with urasil
tRNA- the amino acid that corresponds with mRNA
What is the purpose of DNA polymerase?
Brings in the missing nucleotides and corrects errors made during replication when an incorrect base pair is recognized it reverses its direction by one base pair it then removes the incorrect base and replaces it with the correct one then continues with replication this is called proof reading
What is protein synthesis?
Cells creating protein happens in two major stages transcription and translation
Where does transcription occur?
The nucleus
Where does translation occur?
On ribosomes located in the cytoplasm of the cell or on the rough endoplasmic reticulum in eucaryotic cells
Describe the steps of translation, including tRNA, and amino acids
The TRNA translates the rRNA to amino acids TRNA picks up correct amino acids and recognizes appropriate codons in the mRNA. The tRNA has a single stranded loop called an anticodon. An anticodon triplet is complimentary to the codon triplet on the mRNA. the start code on initiates this process, and when the first anticodon is placed the amino acid corresponding with it forms then, when the next is placed, the previous one breaks off, and another amino acid attaches to the pre-existing, one forming along chain of amino acids, or a polypeptide chain a stop on will be placed, and all the codons will break off, freeing the chain of amino acids to be used in the body
What is the difference between a codon and anticodon?
A codon is a triple code where flow of information from gene to protein is based on it is on mRNA
An anticodon triplet is the complimentary to the codon triplet ob mrna it is found on tRNA
What is the difference between helicase ,polymerase and ligase?
Helicase- it unzips the DNA by breaking the hydrogen bonds
Polymerase– correct errors made during replication when an incorrect base pair is recognized it reverses its direction by one base pair brings in the missing nucleotides
Ligase- repairs, the DNA or joins them back together, fills the gaps between the Okazaki fragments
What is the difference between mRNA and tRNA?
mRNA acts as a messenger carries the genetic code from dna to the ribosomes and communicates the amino acid sequence for protein synthesis
tRNA brings or transports correct amino acids to the growing polypeptide chain to the ribosome for protein synthesis
What is the difference between pyrimidines and purines?
Purines – are double ringed structures like adenine and guanine
Pyrimidines- have a singular ringed structure like cytosine and thymine urasil
What is genetic mutation?
Is a chemical change occurring in the DNA of a cell mutations can cause beneficial and harmful effects on the organisms ability to survive
What is translocation?
Information from one of two homologous chromosomes breaks, and binds to another. Usually the sort of mutation is lethal.
Example)Philadelphia chromosome – affect cells in the bone marrow, which can cause leukaemia
What is deletion?
Certain nucleotides are deleted which affects the coding of proteins that use this DNA sequence, a gene coded for alanine with a genetic sequence of CGG and the cytosine nucleotide was deleted then the alanine amino acid would not be able to be created, and any other amino acids will also be unable to be produced
Example ) Cri-du-chat significant deletion from chromosome. Five babies cry sounds like a cats miaow small head, severe developmental problems really live past one or two.
What is inversion?
Pieces of chromosome break, apart and pieces rejoin the same chromosome in a different order
example ) haemophilia a lack of anti-hemophiliac – globulin a substance needed for normal blood clotting
What is duplication?
When an extra identical piece of chromosome is added to the normal chromosomes
Example ) Charcot, Marie tooth disease – weakness of the foot and lower leg foot deformity, such as high arches and hammer toes, weakness, and muscle atrophy in the hands
What is a frame shift mutation
These are insertions or deletions of more than one base pair in the nucleotide sequence shifts the grouping of these bases and changes. The code for amino acids resulting protein is usually non-functional.
Example ) tay sachs- is fatal because of the inability to break down a lipid death occurs within first year of life
