Gene Expression

What is gene expression?

The process in which a gene is used to produce protein, known as protein synthesis

What are the two main processes involved in protein synthesis?

Transcription and translation

Where are proteins synthesized?

In the ribosomes

What is the structure of DNA?

Double helix shaped with two strands made of repeating nucleotides twisted around each other

What are the components of a nucleotide?

One nitrogen base, deoxyribose sugar, and phosphate groups

What are the four nitrogen bases in DNA?

Adenine, thymine, cytosine, and guanine

What are the base pairing rules in DNA?

A-T C-G

What connects the paired bases in DNA?

Weak hydrogen bonds

What is the difference between the template strand and the coding strand of DNA?

The template strand consists of genetic codes, while the coding strand is the complimentary strand

What is a triplet in the context of DNA?

A triplet is a combination of three DNA bases

What are purines and pyrimidines?

Purines are nitrogenous bases that include adenine and guanine, while pyrimidines are cytosine, thymine, and uracil.

How many hydrogen bonds connect adenine and thymine?

Two hydrogen bonds

How many hydrogen bonds connect guanine and cytosine

Three hydrogen bonds

What is RNA?

RNA is a single-stranded nucleic acid found in the ribosome and cytoplasm

What replaces Thymine in RNA?

Uracil

What are the three types of RNA and their functions?

mRNA copies genetic codes from DNA, rRNA is an essential component of ribosomes, and tRNA transports amino acids to the ribosome for protein synthesis

What is the role of the promoter in transcription?

It signals ‘on’ or ‘off’ for protein synthesis and indicates the start point for transcription

What happens during transcription?

RNA polymerase binds to the promoter, the DNA unzips, the template strand is copied, and mRNA is synthesized

What are codons?

Sequences of three bases in mRNA that code for specific amino acids

What is the start codon?

AUG, where the ribosome binds for translation

What are the stop codons?

UAA, UAG, UGA. The translation process is terminated

How many different amino acids make up human proteins?

20

What is the significance of redundancy in the genetic code?

It allows for substitutions of one base without changing the amino acids, maintaining protein function

What is the process of translation?

The process of assembling amino acids into a protein

What is the structure of tRNa and its function?

It is clover-shaped, and it carries amino acids to the ribosome. The 3 bases of tRNA, called anticodons bond to complementary mRNA codons.

What is the role of the ribosome during translation?

The ribosomes move along the mRNA strand; it reads and matches codons to the corresponding tRNA anticodon

What happens to leftover mRNA after translation?

It is broken down by the enzyme RNAase

Whare the steps involved in protein synthesis?

Step 1: Transcription at the nucleus, where RNA polymerase attaches to the promoter and DNA unzips to make mRNA. Step 2: mRNA detaches and moves to the cytoplasm and ribosome. Step 3: Translation, where tRNA anticodons pair with mRNA codons. Step 4: tRNA brings amino acids to form a polypeptide chain. Step 5: The polypeptide chain detaches when RNAase reaches a stop codon and folds into a protein

What are the two main types of proteins and their functions?

Fibrous, which are rope-like bundles providing mechanical support and contractile functions. Globular which are irregularly folded and have a chemical function

What is the primary protein structure?

The sequence of amino acids connected by peptide bonds

How is the secondary protein structure formed?

It is folded into beta sheets or alpha helices by weak hydrogen bonds between groups of amino acids.

What characterizes the tertiary protein structure?

It is formed by disulfide bonds and hydrophilic/hrdrophopic interactions.

What is the quaternary protein structure?

A structure which consists of globular proteins with with more than one polypeptide chain, such as a hemoglobin, which is composed of 2 alpha and 2 beta polypeptide chains

What are enzymes and their role in biological reactions?

They are globular proteins which act as biological catalysts, they increase rat of reactions

What is the relationship between genes and enzymes?

One gene synthesized only one enzyme, and each enzyme catalyzes one specific type of reactions

What are two types of reactions that enzymes catalyze?

Anabolic (forming large molecules, amino acids making proteins) Catabolic (breakdown of large molecules, eg, glycerol into fatty acids)

What happens to enzymes at high temperatures

It can denature enzymes, causing them to lose their shape and active site

What is a mutation?

A change in gene which resuts in a different DNA base sequence

When do mutations become inheritable?

Mutations must occur during gamete formation in meiosis to be inherited.

What are spontaneous and induced mutations?

Spontaneous mutations result from DNA replication errors, while induced mutations occur when genes are exposed to mutagens

What are mutagens?

Agents which cause mutations, leading to random, non-reversible changes in DNA

What is the difference between amino acids and primary protein structure?

Amino acids are the building blocks of proteins, while the primary protein structure is the specific sequence of these amino acids

What factors can cause enzymes to denature?

High temperature, changes in pH, mutations that alter the active site

What happens when enzymes denature?

They lose their active site and cannot function properly

What are the main types of mutagens?

1. Ionizing radiation (e.g., x-ray, uv radiation) 2. Chemical compounds (e.g., carcinogens, preserved food) 3. Infectious agents (e.g., viruses, bacteria) 4. Alcohol and diet

What is a point mutation?

A mutation which only affects one base of the gene

What are the three types of point mutations?

1. Base substitution 2. Base insertion 3. Base deletion

What is a missense mutation?

A type of point mutation where a base substitution changes a codon potentially, altering protein function

What is a nonsense mutation?

A type of point mutation where a base substitution creates a stop codon, terminating the protein synthesis early

What is a silent mutation?

A mutation that changes genotype but does not affect phenotype

What happens when a base is inserted or deleted from a gene sequence?

It alters the entire sequence of bases, causing a frameshift mutation

What is the impact of a frameshift mutation near the start of a gene?

It is unlikely a functional protein will form

What is the effect of a frameshift mutation near the end of a gene?

A protein may still form and carry out biological functions

What is a genetic disorder?

A phenotype is displayed differently due to a mutation that changes protein function

What causes sickle cell disease?

Changes in the hemoglobin beta gene which causes hemoglobin to crystallize, leading to sickle-shaped red blood cells

What are the consequences of sickle cell disease?

Reduced oxygen-carrying capacity, severe anemia and potential blockage of capillaries

What is metabolism?

Chemical processes in cells that provide energy and products

What is a metabolic pathway?

A sequence of biochemical reactions controlled by enzymes

What happens when the end product of a metabolic pathway accumulates?

Negative feedback occurs to stop the pathway and prevent over-accumulation of products

What is genotype?

The genetic makeup of an individual

How can genotype be changed?

Through gene mutations which can occur spontaneously or due to environmental factors

What are alleles?

Pairs of genes, one inherited from each parent which can be dominant (capital letter) or recessive (lowercase)

What is phenotype?

The observable traits of an individual, influenced by genotype and environmental factors

How do environmental factors affect phenotype?

They can influence traits such as weight, height, and skin colour, changes are not heritable

What is the difference between phenotype and genotype?

Genotype is the genetic makeup, while phenotype is the obeservable expression of that genotype

How can the phenotype of an individual be affected?

By diet, nutrient availability, temperature, sunlight exposure, and pH levels

What are the 3 possibilities of alleles?

Dominant only (e.g., AA dominant allele phenotype)
Dominant + recessive (e.g., Aa dominant allele phenotype)

Recessive allele only (e.g., aa recessive allele phenotype)