SQA course specification unit 1 flashcards

What are the three components of a DNA nucleotide?

A deoxyribose sugar, a phosphate group, and a nitrogenous base.

What forms the sugar-phosphate backbone of DNA?

Alternating deoxyribose sugars and phosphate groups.

How do bases pair in DNA?

Adenine pairs with thymine (A–T), and guanine pairs with cytosine (G–C) via hydrogen bonds.

What is the structural arrangement of the DNA strands?

DNA is double-stranded and antiparallel.

What direction do the DNA strands run?

One strand runs from 5’ to 3’, and the other from 3’ to 5’.

What is the overall shape of DNA?

A double helix.

What is the structure of DNA in prokaryotes?

A single circular chromosome and smaller circular plasmids.

What is the structure of DNA in eukaryotes?

Linear chromosomes located in the nucleus, tightly coiled and packaged with associated proteins.

What types of DNA are found in mitochondria and chloroplasts?

Circular chromosomes

What makes yeast a unique eukaryote?

It also contains plasmids.

What enzyme is essential for DNA replication?

DNA polymerase.

What is the role of primers in DNA replication?

They initiate the addition of DNA nucleotides.

How does DNA polymerase add nucleotides?

It adds DNA nucleotides to the 3’ end of the new strand using complementary base pairing.

What is the role of DNA ligase in replication?

It joins fragments of DNA together.

What does PCR stand for and what does it do?

Polymerase Chain Reaction; it amplifies specific DNA sequences.

How does PCR work?

Repeated cycles of heating (to denature DNA) and cooling (to anneal primers) amplify the target DNA.

What are practical uses of PCR?

Forensics, medical diagnosis, genetic research, and paternity testing.

What are the two main stages of gene expression?

Transcription and translation.

What types of RNA are involved in gene expression?

mRNA, tRNA, and rRNA.

What is the function of mRNA?

It carries a copy of the DNA code from the nucleus to the ribosome.

What is the function of tRNA?

It carries specific amino acids to the ribosome.

How does tRNA maintain its structure?

It folds due to complementary base pairing.

What is the function of rRNA?

It combines with proteins to form ribosomes.

What enzyme carries out transcription?

RNA polymerase

What does RNA polymerase produce?

A primary mRNA transcript.

What is RNA splicing?

The process of removing introns and joining exons in the primary transcript to form mature mRNA.

What are introns?

Non-coding regions of the primary mRNA transcript.

What are exons?

Coding regions that remain in the mature mRNA transcript.

Where does translation occur?

At the ribosome

What signals the beginning of translation?

A start codon

What signals the end of translation?

A stop codon.

How does tRNA match up with mRNA during translation?

Through complementary base pairing between anticodons and codons.

How are amino acids linked during translation?

By peptide bonds.

What happens to each tRNA after it delivers its amino acid?

It leaves the ribosome.

How can one gene produce different proteins?

Through alternative RNA splicing, where different exons are retained.

How are amino acids connected in proteins?

By peptide bonds forming polypeptides.

What determines the 3D shape of a protein?

Folding caused by hydrogen bonds and other interactions between amino acids.

What determines a protein's function?

Its specific 3D shape.

What determines an organism’s phenotype?

The proteins produced as a result of gene expression.

What is cellular differentiation?

A process where cells express certain genes to produce proteins needed for specialized functions.

What are sources of stem cells in plants?

Meristems.

What are embryonic stem cells?

Pluripotent cells that can differentiate into all cell types in the organism.

What are tissue (adult) stem cells?

Multipotent cells involved in growth, repair, and renewal within specific tissues.

What are therapeutic uses of stem cells?

Repairing damaged or diseased tissues or organs.

What are research uses of stem cells?

Studying disease development and drug testing.

What are ethical issues surrounding embryonic stem cells?

Their use involves the destruction of embryos, which raises moral concerns.

What is a genome?

The entire hereditary information encoded in an organism’s DNA.

What do genes code for?

Proteins

What do non-coding DNA sequences do?

Some regulate transcription; other are transcribed but not translated

What is a mutation?

A change in DNA that may alter or prevent the production of a protein

What are single gene mutations

Changes caused by substitution, insertion, or deletion of nucleotides

What are types of nucleotide substitution mutations

Missense
Nonsense
Splice-site mutations

What happens in missense mutations?

One amino acid is changed.

What happens in nonsense mutations?

A premature stop codon is introduced.

What happens in splice-site mutations?

They affect the process of RNA splicing.

What do insertions and deletions cause

Frameshift mutations.

What are chromosome structure mutations?

Duplication, deletion, inversion, and translocation.

Why are mutations important in evolution?

They create variation; gene duplication allows for new functions to evolve.

What is natural selection?

The non-random increase of beneficial DNA sequences and decrease of harmful ones.

What is stabilizing selection?

Favours average traits and reduces variation.

What is directional selection?

Favours one extreme phenotype.

What is disruptive selection?

Favours two extreme phenotypes over the average.

Why is evolution faster in prokaryotes?

They can exchange genetic material horizontally.

What is horizontal gene transfer?

The transfer of genes between organisms in a way other than traditional reproduction.

What is speciation?

The formation of new species through isolation, mutation, and selection.

What prevents gene flow between populations during speciation?

Isolation barriers.

What is allopatric speciation?

Speciation due to geographical barriers.

What is sympatric speciation?

Speciation due to behavioral or ecological barriers.

What does genomic sequencing allow us to do?

Determine the sequence of nucleotide bases in genes or entire genomes.

What does comparing genomes across species reveal?

Many genes are highly conserved.

What is phylogenetics?

The study of evolutionary relationships using DNA sequence data and fossil evidence.

What are molecular clocks used for?

Estimating the timing of evolutionary events.

What are the three domains of life?

Bacteria, Archaea, and Eukaryotes.

How can a genome be used to predict disease?

By analyzing gene variants associated with increased risk.

What is pharmacogenetics?

Using genome data to tailor medical treatments to individuals.

What is personalized medicine?

Medical treatment designed based on an individual’s genome.