DNA & RNA (1.1)

what occurs during cell divison

The chromatin network condenses to form chromosomes which carry the

genetic information of the cell.

where is DNA mainly found?

DNA is found mainly in the nucleus, where it forms part of the

chromosomes and the mitochondria

what is the other name of chromosomal DNA?

nuclear DNA

where does extracellular DNA occur? (2)

occurs in organelles like the mitochondria and chloroplasts.

what do the proteins made by genes determine?

These proteins determine the traits and functions of an organism.

Explain how the work of many scientists contributed to the discovery of the structure of DNA.

Data from X-ray diffraction (Franklin and Wilkins) and model-building (Watson and Crick) together led to the discovery of the double-helix structure of DNA and te base-pairing rule

Why was Watson and Cricks’s work important?

It showed how DNA could replicate and store genetic information

: State ONE contribution made by Maurice Wilkins to the discovery of DNA structure.

He shared data with Watson and Crick.

what is the structure of DNA? (2)

• DNA is made up of two strands that twist around each other to form a double helix shape.

• When untwisted, it looks like a ladder.

what does polymer mean in terms of DNA?

DNA is a type of polymer, which means it’s made up of repeating nucleotides

what are the three parts each nucleotide has?

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

name the four types of nitrogenous bases of DNA

• Adenine (A)

• Guanine (G)

• Cytosine (C)

• Thymine (T).

what does the deoxyribose sugar bond with and form? what does the nitrogenous base attach to?

deoxyribose sugar bonds with the phosphate group, forming the backbone of the DNA strand, and the nitrogenous base attaches to the sugar.

what are the steps of the ‘ladder’ are formed by? (2)

• pairs of nitrogenous bases, which are joined by weak hydrogen bonds.

• Apples in the Tree, Car in the Garage

(base-pairing rule)

how does a gene form a specific protein?

this sequence carries the instructions for the production of proteins by determining the order of amino acids that will join together to form a specific protein.

what happens before cell division and why?

• DNA replicates to make an identical copy of itself.

• This process ensures that the genetic code is accurately passed on from

one generation of cells to the next during growth, repair, and reproduction.

what is the other name for non-coding DNA?

‘junk’ DNA

what is three uses of non-coding DNA

1.) DNA fingerprinting

2.) DNA profiling.

3.) Helps to control the expression of certain genes in coding DNA and protects DNA from mutations (being researched)

This is since it varies greatly before individuals

when does dna replication occur?

during interphase before the cell divides.

what happens during mitosis?

during interphase before the cell divides.

what replicates so that each new cell receives the same genetic information.

DNA

write the process of dna replication (6)

1.DNA unwinds – The double helix uncoils to expose the strands.

2.Strands separate – DNA Polymerase breaks the weak hydrogen bonds between the base pairs.

3.Each strand acts as a template – New complementary nucleotides are added to each original strand.

4.Base pairing occurs – Adenine pairs with Thymine, and Guanine pairs with Cytosine.

5.Sugar and phosphate groups join – They link the new nucleotides into a backbone.

6.Two identical DNA molecules are formed – Each with one old strand and one new strand (semi-conservative replication).

why isn’t mitochondria inherited from ales?

The mitochondria in sperm cells are located in the midpiece, but only the head of the sperm, which contains the DNA, enters the egg during fertilisation. The rest of the sperm, including the mitochondria, is discarded.

why does mtDNA stay relatively unchanged and why is this useful?

• mtDNA does not undergo recombination during meiosis

• makes it useful for studying genetic relatedness among individuals and tracing maternal ancestry

where are the three places RNA is found?

the nucleus and the cytoplasm, and it also forms part of the structure of ribosomes.

what replaces thymine in RNA?

uracil

what happens when nucleotides link together?

the ribose sugar of one nucleotide joins with the phosphate group of the next to form a long single strand

what varies the sequence and number of bases in relation to RNA?

the type and function of the RNA.

what are the three types of RNA?

1.) mRNA

2.) tRNA

3) rRNA

where is mRNA, tRNA and rRNA formed?

mRNA: formed in the nucleoplasm

tRNA: found in the cytoplasm

rRNA: forms part of the structure of ribosomes

Why is Watson and Crick’s model described as a scientific model?

It is a representation of DNA structure based on experimental evidence and can be tested and refined.

Explain why DNA is regarded as an everyday concept.

DNA is used in medicine, forensics, ancestry testing and genetic research.

State ONE reason why there was competition among scientists studying DNA.

Scientists wanted to be the first to explain the structure and function of DNA.

State TWO limitations of DNA models often tested by IEB.

• Models are not to scale (sizes/distances inaccurate)
  • Models are static and do not show dynamic processes like replication or

Name TWO common methods of DNA extraction used in IEB questions.

• Simple household method (detergent, salt, alcohol)
• Laboratory method (enzymes, centrifugation)

Which DNA extraction method is more reliable and why?

The laboratory method because it yields purer DNA, reduces contamination, and is more accurate for scientific analysis.

What does unequal base pairing suggest2?

The nucleic acid may be RNA or single-stranded DNA.

How do antibiotics interfere with protein synthesis?

They block bacterial ribosomes, preventing protein formation and causing cell death.

How did DNA get into mitochondria?

Through endosymbiosis — mitochondria evolved from free-living bacteria.

Why is mitochondrial DNA different from nuclear DNA? (3)

It is circular, smaller, and inherited maternally.

Endosymbiosis ~

a type of symbiosis (mutually beneficial relationship) where one organism lives inside the body or cells of another organism

Why was cracking the DNA code scientifically important?

It explained inheritance, protein synthesis, and genetic disorders.

What is the function of coding DNA?

To determine the sequence of amino acids in a protein.

Why is coding DNA essential? Give THREE reasons.

• Determines which protein is made

• Determines the structure of the protein

• Determines the function of the protein

What does disrupted coding DNA cause?

Mutations that affect protein structure and function.

How does non-coding DNA help regulate gene expression?

It controls when, where, and how much a gene is expressed.

What is the function of gene regulation?

To ensure proteins are produced at the correct time, place, and amount.

Why is non-coding DNA important? (3)

• Regulates gene expression

• Codes for functional RNA

• Provides structural support to chromosomes

Give forms of functional RNA and their roles. (3)

• tRNA – transports amino acids

• rRNA – forms ribosomes

• Regulatory RNA – controls gene expression

Are introns or exons translated?

Exons are translated.

Name the THREE types of non-coding DNA.

• Structural DNA

• Functional RNA genes

• Introns

Where are coding and non-coding DNA found?

Both are found within genes on chromosomes.

: What happens over the years of a person’s life?

Telomeres shorten.

What happens each time a eukaryotic cell divides?

DNA at the ends of chromosomes shortens slightly.

Why is non-coding DNA often used in DNA cloning and restriction enzyme processes? (2)

• Cutting non-coding DNA does not affect protein synthesis

• It reduces harmful mutations