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Year 11 2023 > Human Biology (DNA Replication & Protein Synthesis) > Flashcards

Human Biology (DNA Replication & Protein Synthesis) Flashcards

1
Q

What is DNA?

A

(Deoxyribose Nucleic Acid) A substance that contains the genetic information that determines the structure of the cell and the way it functions.

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2
Q

What is nDNA and where is it located?

A

nDNA is a form of DNA which is a substance that contains genetic information, and is located in the nucleus.

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3
Q

What is mtDNA and where is it found?

A

Small amount of DNA found in the mitochondria, called mitochondrial DNA, or mtDNA, important for the functioning of the mitochondria and, therefore, the cell.

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4
Q

What is DNA made of?

A

Many repeating small units of nucleotides which are composed of a sugar molecule (deoxyribose in DNA), a phosphate group and a nitrogenous base.

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5
Q

What are the 4 different nitrogenous bases?

A
  • Cytosine
  • Adenine
  • Guanine
  • Thymine
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6
Q

What does the sugar molecule of a nucleotide bond to?

A

Sugar molecule of one nucleotide bonds to the phosphate group of another one.

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7
Q

What does the phosphate molecule of a nucleotide bond to?

A

The phosphate group of one nucleotide bonds to the sugar molecule of another one.

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8
Q

What holds two nitrogenous bases together?

A

Weak hydrogen bonds.

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9
Q

What is the complementary base pairing rule?

A

The rule that states that specific nitrogenous bases pair only to their complementary shape pair. That is:

Adenine to Thymine
Guanine to Cytosine

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10
Q

What is a double helix?

A

2 strands of DNA that twist into a spiral shape.

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11
Q

What determines genetic code? What is the length of an average DNA in a cell?

A

The order in which the nitrogenous bases occur in the DNA molecule determines the genetic code. Molecules of DNA are in the form of long strands – between 2 and 3 metres in a human cell.

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12
Q

What is a nucleosome?

A

DNA strands that are wrapped around a group of eight special proteins called histones to form a nucleosome.

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13
Q

What shape is the DNA molecule that is not dividing in?

A

In a cell that is not dividing, the coiled DNA forms a tangled network called chromatin.

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14
Q

What shape is the DNA molecule that is dividing in?

A

In a cell that is diving, the coiled DNA forms chromosomes.

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14
Q

What is the number of chromosomes in the average human cell?

A

46

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15
Q

What do the sections of chromosomes do?

A

Each chromosome is made up of sections of DNA that code for a particular protein called a gene.

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16
Q

What are histones?

A

Special proteins that DNA is wrapped around and coiled in.

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17
Q

What are 2 differences between Mitochondrial and Nuclear DNA?

A

Nuclear DNA is in the form of very long strands that are bound to proteins, the histones, while mitochondrial DNA is in the form of small circular molecules that are not bound to proteins.

NDNA is found in the nucleus, while mtDNA is in the mitochondrion.

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18
Q

~ How many molecules and genes of mtDNA are in each mitochondrion?

A

5 - 10 molecules

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19
Q

How many genes are used for making tRNA (Transfer RNA)?

A

24 genes

20
Q

How many genes are responsible for making some of the enzymes needed for the reactions in cellular respiration?

A

13 genes.

21
Q

What is the first part of DNA replication?

A

When the two strands of the DNA molecule are separated by the enzyme helicase. Helicase breaks the hydrogen bonds between the bases.

22
Q

What is the second part of DNA replication?

A

When the two enzymes DNA Polymerase and DNA Ligase work together to build the new strand.

Specifically:

Polymerase: Adds the new nucleotides to the new strand and joins them together with hydrogen bonds.
Ligase: joins short sections of DNA together by reattaching the phosphate and deoxyribose backbone.

23
Q

What are the features of the newly made DNA after DNA replication?

A

As the base adenine can only pair with thymine, and cytosine can only pair with guanine, the new strand that forms is identical to the original.

Each starnd of the separated section contains only half of the original information.

24
Q

What is Protein Synthesis?

A

Process of proteins being produced from amino acids being joined together by peptide bonds.

25
Q

How does the sequence of DNA order affect protein synthesis?

A

The sequence of bases in DNA controls the order of amino acids, and therefore the type of protein that is produced.

26
Q

List 3 common proteins?

A
  • Haemoglobin
  • Actin and Myosin
  • Collagen
27
Q

What is RNA, and its difference to DNA?

A

Ribonucleic Acid, is another type of nucleic acid found in the body.

Some key differences;
The sugar molecule is ribose, not deoxyribose. Ribose has one more oxygen atom than deoxyribose.
RNA is single stranded, while DNA is double stranded
Replaced Thymine with Uracil

28
Q

How does RNA form hydrogen bonds?

A

The RNA strand is able to fold on to itself, forming hydrogen bonds between complementary bases.

29
Q

What are the different types of RNA?

A

There are 3 different types:

  • Messenger RNA (mRNA)
  • Ribosomal RNA (rRNA)
  • Transfer RNA (tRNA)
30
Q

What does mRNA do?

A

(mRNA) is made in the nucleus and takes the genetic code into the cytoplasm. It is read by the rRNA in the process of protein synthesis.

31
Q

What does rRNA do?

A

The rRNA ensures the correct alignment of mRNA, tRNA and ribosome. It also has an enzymatic role in the formation of peptide bonds between amino acids.

32
Q

~ How much of the mass of ribosomes is made of rRNA?

A

Makes up approximately 60% of the mass of ribosomes, with the other 40% being protein.

33
Q

What does tRNA do?

A

A small molecule of RNA, containing only 70–90 nucleotides. Each tRNA molecule is able to carry a specific amino acid and therefore plays a vital role in protein synthesis.

34
Q

What is a triplet?

A

A sequence of three bases on DNA that code for a particular amino acid. A three-nucleotide sequence that is unique to an amino acid.

35
Q

What is a codon?

A

A triplet that is found on mRNA.

36
Q

Wha is the difference between a triplet and a codon?

A

A triplet is found on DNA, while a codon is in referral to mRNA.

37
Q

What is Transcription?

A

Process by which the genetic instructions are copied (or transcribed) from the DNA to the mRNA molecule.
Triggered by chemical messengers that enter the nucleus from the cytosol and bind to the DNA at the relevant gene.
Causes an enzyme called RNA polymerase to begin the process of making mRNA.

38
Q

What are the steps involved in transcription?

A

First, the helicase enzyme makes the double-stranded DNA molecule come apart, usually separates about 17 base pairs at a time.

RNA polymerase then transcribes (copies) the bases on one strand of the DNA to make a complementary molecule of mRNA.

At the end of the gene, a sequence of bases tells the RNA polymerase to stop copying, and as a result the mRNA molecule is released.

Often other RNA polymerases will follow the first one, so that many copies of the same mRNA are made.

Only one of the strands of the DNA molecule is copied during transcription. This is called the template strand because it is the template from which the mRNA is made. The other DNA strand is known as the coding strand.

39
Q

What is Translation?

A

Production of a protein using the information that is coded in the mRNA molecule.

In the cytosol, a ribosome attaches to one end of the mRNA molecule at a particular sequence of bases (adenine, uracil, guanine) called the start codon, which ensures that the ribosome attaches to the correct end of the mRNA.

Ribosome then moves along the mRNA three bases at a time.

As the ribosome reads the codons on the mRNA, the tRNA molecules with the complementary bases join the mRNA.

The amino acids carried by the tRNA are joined so that the protein is assembled with the amino acids in the correct sequence.

For each bond formed between the amino acids, the energy from the breakdown of one ATP molecule is required.
Once the tRNA has delivered its amino acid, it detaches from the ribosome and can then pick up another amino acid from the cytosol.

40
Q

What is a codon and anticodon?

A

Each group of three bases is called a codon and corresponds to a specific amino acid.
The sequence of three bases matching the codon is called the anticodon.

41
Q

What is Gene Expression?

A

The process of copying information from DNA on to messenger RNA (mRNA) and then translating the message into a series of amino acids to form a protein is called gene expression.

” Gene expression is the process by which the instructions in our DNA are converted into a functional product, such as a protein.”

Only certain genes are transcribed in each cell. Genes are switched on or off in accordance with the type of cell and its activity.

42
Q

What is specific about Lipid and Carbohydrate Synthesis?

A

No genes that carry instructions for the manufacture of lipids or carbohydrates.

Synthesis of these substances requires enzymes, and enzymes are proteins.

The DNA in the genes carries the code for protein manufacture, therefore the genes indirectly control the synthesis of lipids and carbohydrates.

43
Q

What is Epigenetics?

A

Refers to changes in gene expression that result from mechanisms other than changes in the genes – that is, in the DNA or genome.

An important area of research where scientists try to find out the factors that help to make us who we are and influence what diseases we might acquire.

44
Q

What is an Epigenome?

A

Epigenome is the sum of all the factors that determine when, where and which genes are ‘switched on’ or expressed, helps to control which genes are active in a particular cell and therefore which proteins will be produced.

One way in which genes are regulated epigenetically is through changes in chromatin.

45
Q

How does Chromatin shape affect the gene expression?

A

Gene expression may change if the way in which the DNA is wrapped around the histone changes. There are a number of ways a change in the structure of the chromatin can occur.

If some of the amino acids that are in the histone proteins are changed, this will change the shape of the histone.

“However, loose the chromatin is around the histones it is better for gene expression.”

46
Q

What is the 2 ways that Chromatin can be altered to change gene expression?

A

Acetylation – the addition of an acetyl group to the histone protein. Acetylation relaxes the chromatin and increases transcription, enhancing gene expression.

Methylation – the addition of methyl groups to the DNA molecule or histone proteins. Histone methylation may either increase or decrease the transcription of genes, depending on where the methyl groups attach and how many become attached.

47
Q

What are some ways the environment affects a person’s epigenomes?

A

A person’s epigenome can be changed by exposure to certain environmental stimuli.

Examples of environmental agents that may cause epigenetic changes are severe stress, nutritional factors, and toxins or drugs that may enter cells.

Such agents do not change the DNA, but they interfere with the transcription and translation processes involved in protein production

Year 11 2023 (29 decks)

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