Higher Biology - Unit 1

What is the structure of DNA?

DNA is a double helix made of two antiparallel strands of nucleotides.

What are the three components of a nucleotide?

Deoxyribose sugar, phosphate group, and nitrogenous base.

What are the four bases found in DNA?

Adenine, Thymine, Guanine, Cytosine.

What is the complementary base pairing rule?

A pairs with T, G pairs with C.

What type of bond joins complementary bases?

Hydrogen bonds.

What makes up the sugar-phosphate backbone of DNA?

Deoxyribose sugars and phosphate groups.

What does antiparallel mean in DNA strands?

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

Where is DNA found in prokaryotes?

In a single circular chromosome and in plasmids.

Where is DNA found in eukaryotes?

In linear chromosomes in the nucleus and in circular chromosomes in mitochondria and chloroplasts.

What are histones?

Proteins that DNA coils around in eukaryotic chromosomes.

What is special about yeast as a eukaryote?

It contains plasmids like prokaryotes.

What enzyme is responsible for DNA replication?

DNA polymerase.

What is a primer?

A short strand of nucleotides that allows DNA polymerase to start replication.

What is the leading strand?

The DNA strand replicated continuously.

What is the lagging strand?

The DNA strand replicated in fragments.

Why is the lagging strand replicated in fragments?

DNA polymerase can only add to the 3' end, so replication is discontinuous.

What enzyme joins fragments of DNA on the lagging strand?

Ligase.

What is the role of ATP in DNA replication?

Provides energy for the process.

What is PCR used for?

To amplify DNA for forensics, disease diagnosis, and paternity tests.

What temperatures are used in PCR?

92–98°C to separate strands, 50–65°C for primers to bind, 70–80°C for replication.

What is Taq polymerase?

A heat-tolerant DNA polymerase used in PCR.

What is the structure of DNA?

A double helix made of two antiparallel strands of nucleotides.

What are the components of a DNA nucleotide?

Deoxyribose sugar, phosphate group, and a nitrogenous base.

What are the nitrogenous bases in DNA?

Adenine, Thymine, Guanine, Cytosine.

What base pairs with Adenine in DNA?

Thymine.

What base pairs with Guanine in DNA?

Cytosine.

What type of bond holds DNA bases together?

Hydrogen bonds.

What is the sugar-phosphate backbone?

The structural framework of DNA made from sugar and phosphate groups.

What is meant by DNA strands being antiparallel?

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

Where is DNA found in prokaryotes?

In a single circular chromosome and plasmids.

Where is DNA found in eukaryotes?

In linear chromosomes in the nucleus and circular chromosomes in mitochondria and chloroplasts.

What proteins help package DNA in eukaryotes?

Histones.

What is unique about yeast's DNA?

Yeast has plasmids like prokaryotes.

What is a gene?

A DNA sequence that codes for a protein.

What enzyme is responsible for DNA replication?

DNA polymerase.

What is a primer in DNA replication?

A short strand of nucleotides allowing DNA polymerase to start replication.

In which direction does DNA polymerase work?

5' to 3' direction.

What is the leading strand?

The DNA strand replicated continuously.

What is the lagging strand?

The DNA strand replicated in fragments.

What enzyme joins DNA fragments?

Ligase.

What energy molecule is needed for DNA replication?

ATP.

What is PCR used for?

To amplify DNA for forensics, diagnostics, or research.

What are the three temperature stages of PCR?

92–98°C denature, 50–65°C anneal, 70–80°C extend.

What is Taq polymerase?

A heat-tolerant enzyme used in PCR.

What is gene expression?

The transcription and translation of DNA into proteins.

What are the types of RNA?

mRNA, tRNA, rRNA.

What base replaces thymine in RNA?

Uracil.

What does mRNA do?

Carries the DNA code from the nucleus to the ribosome.

What is a codon?

A triplet of bases on mRNA coding for an amino acid.

What is tRNA?

RNA with an anticodon and amino acid attachment site.

What does rRNA do?

Forms part of the ribosome with proteins.

What enzyme makes mRNA?

RNA polymerase.

What is the primary transcript?

The initial mRNA made from DNA.

What is RNA splicing?

Removal of introns and joining of exons.

What is the mature transcript?

mRNA with exons only.

What is translation?

Process of making a protein from mRNA.

What bonds link amino acids?

Peptide bonds.

What determines protein shape?

Amino acid interactions and folding.

What is a phenotype?

The physical expression of a gene.

What is cellular differentiation?

Process by which cells express certain genes to perform specific functions.

Where does differentiation occur in plants?

Meristems.

What are meristems?

Regions of unspecialised cells in plants.

What are apical meristems?

Found at tips of shoots and roots.

What are lateral meristems?

Found within the stem.

What are stem cells?

Unspecialised animal cells that can divide or differentiate.

What are embryonic stem cells?

Pluripotent cells that can become any cell type.

What are tissue stem cells?

Multipotent cells for specific tissue types.

Give an example of a multipotent stem cell.

Blood stem cells producing blood cell types.

What is a therapeutic use of stem cells?

Regenerating damaged tissues or organs.

What are ethical issues of embryonic stem cells?

Involves destruction of embryos.

What can stem cell research help with?

Studying cell growth, disease, and drug testing.

What is the genome?

An organism’s complete set of DNA.

What are genes?

DNA sequences that code for proteins.

What is the function of non-coding DNA?

Regulates transcription or forms RNA like tRNA/rRNA.

What is a mutation?

A change in DNA sequence.

What are the three single-gene mutation types?

Substitution, insertion, deletion.

What is a missense mutation?

One amino acid is replaced with another.

What is a nonsense mutation?

A codon changes to a premature stop codon.

What is a splice-site mutation?

A mutation affecting RNA splicing.

What are frameshift mutations?

Mutations that alter the reading frame (insertion/deletion).

Give an example of a deletion disorder.

Cystic fibrosis.

Give an example of an insertion disorder.

Tay-Sachs disease.

What are the four types of chromosome mutations?

Duplication, deletion, inversion, translocation.

What is a duplication mutation?

Section of a chromosome is copied.

What is a deletion mutation?

Section of a chromosome is lost.

What is an inversion mutation?

Section of chromosome is reversed.

What is a translocation mutation?

Section added to a different, non-homologous chromosome.

Why are chromosome mutations often lethal?

They cause substantial genetic changes.

What is the benefit of duplication mutations?

They allow new genes to evolve while originals remain functional.

What is evolution?

Change in organisms over generations due to genetic variation.

What is natural selection?

Increase of traits aiding survival and decrease of harmful traits.

What is stabilising selection?

Selection for average traits.

What is directional selection?

Selection for one extreme trait.

What is disruptive selection?

Selection for two or more extreme traits.

What is horizontal gene transfer?

Genes transferred between individuals of the same generation.

What is vertical gene transfer?

Genes passed from parent to offspring.

Why is evolution faster in prokaryotes?

They can exchange genes horizontally.

What is a species?

A group that can interbreed and produce fertile offspring.

What is speciation?

Creation of new species through isolation and evolution.

What is allopatric speciation?

Speciation due to geographical barriers.