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Higher Biology > Unit 1 > Flashcards

Unit 1 Flashcards

1
Q

What does a DNA nucleotide look like?

A

Deoxyribose sugar with base attached to carbon 1 and a phosphate group attached to carbon 5.

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2
Q

How is the sugar phosphate backbone made?

A

Chemical bonds form between the phosphate of one nucleotide and carbon 3 of anther nucleotide.

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3
Q

Describe the structure of DNA

A

DNA consists of two strand. Each composed of repeating units called nucleotides which run and antiparallel directions that form a twisted coil called a double helix

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4
Q

Describe a prokaryotic cell.

A

Lacks a membrane bound nucleus.
DNA is stored in the cytoplasm in the form of a large circular chromosome but also has smaller rings of DNA called plasmids.

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5
Q

Describe a eukaryotic cell

A

Has a membrane bound nucleus that stores genetic information. The DNA is tightly coiled into linear chromosomes which can be found in the nucleus as well as other cell organelles in the form of circular chromosomes. These circular chromosomes code for proteins to be synthesised for that specific organelle.

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6
Q

Give 5 requirements for DNA replication.

A 
DNA 
primers 
Enzymes ( Ligase and DNA polymerase )
ATP
Nucleotides.
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7
Q

In what direction does DNA polymerase add DNA nucleotides?

A

3’-5’

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8
Q

Why can DNA replication be described as semi-conservative ?

A

Because once replicated, the daughter cell has one new strand of DNA and one parent strand

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9
Q

What is PCR

A

The amplification of a piece of DNA. It is short for the polymerase chain reaction.

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10
Q

What allows PCR to be highly specific on a particular piece of DNA?

A

The fact that primers can be selected to be complementary to a specific target sequence.

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11
Q

Why can PCR be described as thermal cycling ?

A

The DNA is heated and cooled repeatedly.

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12
Q

Describe the thermal cycling process in PCR

A

The DNA is heated to 95 degrees to break the weak hydrogen bonds between base pairs.
It is cooled to 60 degrees to allow the primers to anneal to the strand. It is heated to 70 degrees to allow TAQ polymerase to create an extension of nucleotides from the primer.

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13
Q

How many molecules of DNA are produced from the first cycle of PCR ?

A

One new copy is produced so altogether 2.

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14
Q

Give 3 practical Applications of PCR.

A

Can be used to: create DNA fingerprint from DNA collected at a crime scene
Preserve the remains of an ancient species.
Replicate viruses for research

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15
Q

What is RNA splicing?

A

The cutting of introns from a primary transcript of Rna and the joining together of exons to produce the mature transcript.

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16
Q

Where does the first stage of protein synthesis take place and what is it called?

A

Transcription and takes place in the nucleus.

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17
Q

What is the second stage of protein synthesis called and where does it take place ?

A

Translation and it takes place at a ribosome.

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18
Q

Describe the structure of rna and give examples of it.

A

Composed of nucleotide molecules of ribose sugar bonded to a phosphate group and a base ( AU, CG) unlike DNA it is single stranded.
Types of rna include tRNA mRNA and rRNA ( all have individual functions)

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19
Q

Give an example of post transcription modification of an mRNA molecule.

A

Alternative RNA splicing (different sequences of introns and exons are joined together when making mature transcript of mRNA)

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20
Q

Give 2 examples of post translational modification of mRNA.

A 
Cleavage 
Molecular addition ( adding carbohydrates and phosphates )
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21
Q

What does the modification of a protein allow?

A

Many proteins to be synthesised from the same gene.

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22
Q

Give he differences between DNA and rNA

A

DNA is doubly stranded where as RNA is single
In DNA : AT CG in RNA: AU CG
DNA contains deoxyribose sugar. RNA contains ribose sugar.

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23
Q

What is cellular differentiation?

A

The process by which an unspecialised cell becomes specialised.

24
Q

What is gene expression ?

A

The process by which genes are switched on and off

25
Q

As well as gene expression, what is the phenotype of an organism influenced by ?

A

Intra and extra cellular environmental factors

26
Q

What is gene expression controlled by ?

A

The regulation or transcription and translation.

27
Q

What are meristems.

A

Region of unspecialised cells in plants that are capable of cell division

28
Q

What are stem cells?

A

Unspecialised somatic cells that are able to divide and differentiate.

29
Q

What is the difference between embryo and tissue stem cells ?

A

Embryonic stems cells are pluripotent and can be found in the early stages of an embryo.
Adult tissue stem cells are multi potent and can be found in bone marrow

30
Q

What is meant by the genome.

A

All an organism’s hereditary information

31
Q

What does the structure of the genome consist of ?

A

Coding and non coding regions

32
Q

What types of RNA are transcribed but never translated ?

A

tRNA, rRNA, RNA fragments

33
Q

What are the 3 types of single gene mutations?

A

Gene-
Substitution
Deletion
Insertion

34
Q

What are the 3 types of chromosome mutations?

A 
Chromosome- 
Duplication 
Deletion 
Inversion
Translocation.
35
Q

Why are mutations important for evolution?

A

Duplication produces a second copy of a gene which is free from selection pressure which means it can mutate to provide new DNA sequences.
This can give organisms an advantage to increase heir fitness and chances of survival.
It is the only source of new variation.

36
Q

What is polyploidy?

A

The duplication of all the chromosomes resulting in a cell with an extra set of chromosomes. It is the result of an error during he separation of chromosomes during cell division.

37
Q

Why is polyploidy important in plants and the evolution of animals?

A

Plants - polyploidy plants are usually bigger + have increased seed size which is of economic importance
Animals- mammals which are polyploidy usually fail to survive.

38
Q

What are genomic variations ?

A

The changes in frequency of certain alleles

39
Q

In what 2 main ways can gene transfer occur ?

A

1- vertical gene transfer

2- horizontal gene transfer ( prokaryotes )

40
Q

In what 2 ways can vertical gene transfer take place ?

A

Sexual and asexual reproduction

41
Q

In what 3 was can horizontal gene transfer take place ?

A

1- transformation
2- transduction
3- conjunction

42
Q

How are the two anti parallel in a DNA molecule held together?

A

Weak hydrogen bonds between base pairs.

43
Q

What is a nonsense mutation?

A

When a codon that are used to code for an amino acid mow codes for a stop codon as a result of a mutation this causes protein synthesis to be stopped prematurely making the protein shorter.

44
Q

What is a missense mutation?

A

Following a substitution mutation, and the altered codon still codes for an amino acid which still makes sense but not the original sense

45
Q

What is a splice site mutation ?

A

A splice site mutation is one which substitutes, deletes or inserts one or more nucleotides at a site where introns are usually removed from a primary mRNA transcript. This results in a protein that doesn’t function properly.

46
Q

Give 2 types of selection in evolution.

A

Natural and sexual.

47
Q

What types of selection is possible for a quantitative trait ?

A

Disruptive, directional, stabilising.

48
Q

What is genetic drift and what is it caused by?

A

The random increase and decrease of alleles particularly in small groups
It is the result of neutral mutations and founder effects.

49
Q

How is a species defined?

A

A species is a group of animals capable of interbreeding and producing fertile offspring.

50
Q

What is speciation and what are the 3 main events ?

A

Speciation is the generation of a new species over a long period of time from one original species. The process includes isolation, mutations and selection.

51
Q

What is the deference between allopatric and sympatric speciation?

A

In allopatric speciation the barrier is geographical

In sympatric speciation the barrier is behavioural.

52
Q

What is the role of barriers in speciation?

A

They prevent gene flow between two groups.

53
Q

What is a hybrid zone?

A

Zones of interbreeding between closely related members of a species that allows gene flow between sub-populations

54
Q

What is genomic sequencing ?

A

It involves working out sequences of nucleotides for individual genes and entire genomes.

55
Q

What is used to determine events in evolution?

A

Sequence data and fossil evidence

56
Q

What is phylogenetics?

A

The comparing of genes to determine the relatedness of different organisms.

Higher Biology (3 decks)

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