Stage 2 - DNA and Proteins

What does DNA stand for

Deoxyribonucleic acid

DNA can self-replicate: true or false

True

genetic code is different on all living things: true or false

false

what is a codon

3 bases that direct protein synthesis

what are nucleic acids

long molecules made up of nucleotides

what are nucleotides

subunits

three kinds of nucleotides are:

Sugar, phosphate group, nitrogen base

What are the four bases in DNA

Thymine, Guanine, Cytosine, Adenine

What are the four bases in RNA

Guanine, Cytosine, Adenine, Uracil

What base replaces Thymine in RNA

Uracil

what sugar is found in RNA

ribose sugar

what sugar is found in DNA

Deoxyribose sugar

how many chromosomes does a prokaryotic cell have

1

what is the shape of a prokaryotic chromosome

circular

Where is the chromosome in a prokaryotic cell

Cytoplasm

How is mitochondrial/chloroplast DNA different from nuclear DNA

Does not contain histones

True or false: Mitochondrial DNA looks the same as prokaryotic DNA

true

What shape are eukaryotic chromosomes

linear

What is the name of the protein the nuclear DNA is curled around

Histones

How many chromosomes do humans have

46 (23 pairs)

what are enzymes

biological catalysts

What do enzymes do

Speed up metablolic reactions without being consumed

What is activation energy

the initial input of energy required for reaction to begin

True or false: enzymes raise the amount of energy required for action

false

What is the induced fit model for enzymes

The enzyme adjusts to better fit the substrate

What does the induced fit of the enzyme do?

places stress on chemical bonds

Why is it good that enzymes place stress on chemical bonds

makes substrate easier to break down

What happens when enzymes are below their optimal temperature?

molecules move slower and are less likely to collide

What happens when enzymes are above their optimal temperature?

enzyme denature

What happens when enzymes denature

H bonds are disrupted and enzyme is no longer complementary to substrate

What affect can the wrong pH have on enzymes

Could cause the unfolding of the enzyme as the H bonds are breaking

How does a competitive inhibitor stop the induced fit model

They have a complementary shape to active site and bind to it, preventing substrate from doing so

How does a noncompetitive inhibitor stop the induced fit model

They bind to the enzyme (not in active site) and change the active site shape to make it no longer complementary to the substrate

What is the point of saturation

enzyme active sites are all occupied and rate of reaction plateaus

What are some protein functions?

Catalyse reactions, movement, defence, structural, transport, communication

Name a protein that aids in catalysing reactions

enzymes

Name a protein that aids in movement

muscles

Name a protein that aids in defence

antibodies

Name a protein that aids in structure

Hair, nails, muscle

Name a protein that aids in transport

blood carrying oxygen

Name a protein that aids in communication

hormones

How do many enzymes function

Recognising and binding to specific molecules in 3D complementary manner

What are antibodies

proteins produced by B cells

What are proteins made up of

1 or more polypeptide chains

what are polypeptide chains made up of

different amino acids

What is the primary structure of a protein

sequence of amino acids in polypeptide chain

what does primary structure dictate in a protein

how it folds and functions

What is the protein's primary structure determined by

the sequence of bases on mRNA which is decided by DNA base sequence

What is the secondary structure of a protein

coiling or folding of sections of polypeptide chain into helices and sheets

What is the protein's secondary structure determined by

unique sequences on primary structure that coil and fold - held together by hydrogen bonds

how does the secondary structure of a protein form

the amino acids are attracted to one another

What is the tertiary structure of a protein

The 3D shape of a single polypeptide chain

What is the tertiary structure of a protein determined by

secondary structure which is affected by primary structure and gene sequence

What is the quaternary structure of a protein

3D shape of two or more polypeptides

What is the quaternary structure of a protein determined by

Interactions between the polypeptides, enabling formation of chemical bonds

How do multicellular organisms begin

As undifferentiated cells

How do cells differentiate

zygote divides by mitosis and daughter cells differentiate

What are undifferentiated cells called

stem cells

What are the processes involved in gene expression

transcription and translation

what is a phenotype

physical characteristics of an individual

what is a genotype

particular set of genes an organism has for traits

what is a popular way to map genotypes

punnet squares

What are the factors that can alter gene expression

environment, products of genes, DNA methylation, epigenetic, histone modification

What ar the environmental factors that can alter gene expression

temperature and UV

what are some products of genes

activator proteins and repressor proteins

What do activator proteins do

switch genes on by by binding to DNA promoter region, allowing RNA polymerase to bind and activate transcription (increasing gene expression)

What do repressor proteins do

Switch genes off by blocking RNA polymerase attachment (decreasing gene expression)

how does miRNA prevent translation

by binding to mRNA, stopping it from binding to ribosome

how does siRNA stop translation

degrades the mRNA

What is DNA methylation

an epigenetic change

what happens when DNA methylation occurs

there is an addition of methyl group to cytosine nucleotides, deactivating genes

what is the chemical sign for methyl group

-CH3

What does an increase of methylation do to RNA

prevents it from binding and transcribing

What are histones

protein that helps package DNA

what can happen if histone is modified

cells regulate gene expression

true or false: DNA that is loosely packaged is easier to express

true

What are the amino acid chains that extend from histone protein

tails

how can the amino acid tails be modified

by attaching chemical tags

What are epigenetic

long term inheritable changes in gene expression that doesn't change DNA sequence

who inherits epigenetic

daughter cells

True or false: epigenetic cannot distinguish cells from one tissue to another

false

What can epigenetic changes lead to

cancer (uncontrolled cell growth)

What are the two ways epigenetic changes can lead to cancer

deactivating timor suppressor genes (preventing cell division) and activating oncogenes (promoting cell division)

What are mutations

random and permanent changes in the sequence of nucleotides in DNA

when can spontaneous mutations occur

DNA replication (mistakes cells don't notice), Cell division (mitosis/meiosis)

How can mutations by induced

through ionising radiation, mutagenic chemicals, some viruses

state an example of ionising radiation

X-rays, UV, gamma rays

state an example of mutagenic chemicals

cigarette smoke

How can viruses lead to mutation cell

some viral DNA becomes incorporated into host cell

step 1 of error in DNA replication

DNA polymerase mismatches DNA complementary base pairs

When does an error in DNA replication occur

when bases are exposed and vulnerable

step 2 of error in DNA replication

insertion on incorrect base

step 3 of error in DNA replication

upon further replication, the base is permanently changed in DNA base sequence on both strands

State the types of mutations

insertion, deletion, substitution

what kinds of mutations change the reading frame

insertion and deletion

when do chromosomal mutations occur

during cell division

what causes chromosomal mutations

chromosomes don't seperate properly

what is the result of chromosomal mutations

cells receive extra or are missing chromosomes

What are germ cells

gametes or cells that divide by meiosis to produce gametes

what are somatic cells

cells that don't lead to gametes