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Science 2016 > DNA and Genetics > Flashcards

DNA and Genetics Flashcards

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1
Q

DNA

A

Stands for deoxyribonucleic acid. A molecule that determines the characteristics of living things

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2
Q

Sexual reproduction

A

Sexual reproduction creates variation in a population. It is the role of the female and male reproductive system to ensure that:

  • the male and female gametes meet
  • fertilisation takes place
  • the new individual has the best chance of survival
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3
Q

Process of sexual reproduction

A

The process involves two parents. Both parents contribute one gamete ensuring genetic information is obtained equally from each parent. The female gamete, egg, and the male gamete, sperm are each formed in specialised reproductive systems and when they meet, fertilisation occurs.

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4
Q

Franklin and Wilkins contribution to DNA

A

Early 1950s, Rosalind Franklin, British scientist and X Ray crystallographer and fellow worker Maurice Wilkins made X-ray images of DNA. The famous photograph, photo 51 showed an X pattern. The two scientists deduced that DNA contained rungs like a ladder and the X shape showed it was a helix. This was the closest they came to discovering the DNA structure. Watson and Crick used Franklin’s research and she was never acknowledged until 1968, by then she was dead and didn’t receive a NPP like the others

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5
Q

Watson and Crick contribution to DNA

A

1953, molecular biologists, Watson and Crick used Franklins research and findings to refine their 3D DNA model. They used parts of franklins image to piece together their attempt at finding the structure of DNA. They discovered DNA was a double helix figure and it is now called the Watson- Crick model. In 1965, they won a Nobel peace prize.

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6
Q

DNA structure

A

Made up of smaller sections called nucleotides, arranged in double helix shape

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7
Q

Nucleotides

A

The parts of DNA that make the ladder. 3 main sections:

  • phosphate
  • deoxyribose sugar and nitrogen rich bases
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8
Q

Phosphate and deoxyribose sugars

A

Make the upright part of the ladder. Alternate between phosphate and sugar. The bases always connect to the sugar

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9
Q

Bases

A

Nitrogen rich bases make the rungs of the ladder. Four bases all have different chemical structures. A T C G

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10
Q

Complementary base pairing

A

The bases have different chemical structures meaning they can only pair up in one way.
A with T
C with G
Only two types of rungs on the ladder, AT and CG rungs

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11
Q

AT bases

A

Adenine and thymine, pair up together to make rungs on the ladder

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12
Q

GC bases

A

guanine and cytosine pair up to make CG rungs

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13
Q

chromosomes

A

Humans are made up of cells which have a nucleus. In the nucleus are thin thread like structures called chromosomes. Chromosomes are made up of DNA and proteins. Each cell contains 46 chromosomes in 23 pairs except gametes (only have 23) and red blood cells (don’t have a nucleus)

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14
Q

Genes

A

Sections of DNA. Each chromosome can have over 1000 genes.

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15
Q

Difference between one gene and the next

A

Order of bases along the DNA strand

Length of the DNA strand

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16
Q

Order of bases along DNA and egs,

A

This is the genetic code. Each code contains instructions for a specific protein:

  • Collagen (ligaments, tendons)
  • Keratin (hair, skin)
  • Amylase (saliva)
  • Hormones
  • Insulin
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17
Q

DNA replication

A

The process of copying DNA
The parent DNA starts to separate and unzip like a zipper. Nucleotides that are not part of DNA but in the nucleus join to exposed bases (exposed form unzipping). The sugar and phosphate bond with neighbouring nucleotides. A new identical strand of DNA is formed.

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18
Q

Chromatid

A

One half of the chromosome. Each chromosome is made up of two chromatids joined together. Each chromatid is a double helix of DNA

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19
Q

XY

A

Boy

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20
Q

XX

A

Girl

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21
Q

Mitosis

A

A process of asexual reproduction in which the cell divides in two, producing a replica with an equal number of chromosomes in each, resulting in a diploid cell. Occurs for cellular reproduction and general growth and repair. Creates everything other than sex cells.

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22
Q

Mitosis stages

A

Produced differently to only have half the chromosomes.
Replication of chromosomes to become double stranded. The chromosomes become visible and recombination occurs: swapping of parts of DNA. The chromosomes are pulled apart and two cells are made. This occurs again, new nuclei form around the four new cells which are all genetically different and have half the no. Of chromosomes. These are gametes.

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23
Q

Meiosis

A

Division of sex cells, produces gametes, has half the number of chromosomes and this is where variation of genetic information is created.

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24
Q

Meiosis stages

A

Chromosomes replicate to become double stranded. These chromosomes aren’t necessarily identical to each other: eg RR and rr. The nuclear membrane breaks down and homologous pairs of chromosomes line up on the equator of the cell. Fibres extend from the poles of the cell to each chromosome pair. When they contract, one chromosome from each pair moves to opposite ends of the cell. Two cells are formed and each chromosome is still two chromatid. New fibres from poles (at right angles to the last) attach to chromosomes lined up at the equator. When the fibres contract,chromatids are pulled towards the poles of the cells. There are now bundles of 23 chromosomes, membranes are formed and the cytoplasm divides resulting in 4 new cells, containing the haploid number of chromosome. These cells are not identical. Eg: R, r, R, r. They carry the information about the same characteristics but the specific information is different. These are the gametes.

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25
Diploid number
No. Of chromosomes in your body cells. 46, aka 2N (2 sets of 23)
26
Gametes
Sex cells. Half the diploid number. When the egg and sperm meet, then a full set is made of the two sets of 23 chromosomes
27
Sex chromosomes
Of the 46 chromosomes in your cells, 2 are sex chromosomes. The ones that determine whether you are male or female.
28
Autosomes
The other 44 chromosomes that arent sex chromosomes. They are grouped into 22 pairs. Chromosomes in a pair are homologous (same)
29
Homologous chromosomes
The same. Same length Same centromere (where the two chromosomes join) in the sane position Same location along length for particular characteristics
30
Haploid no.
No, of chromosomes in each gamete, 23, known as N
31
Haploid cell
A cell that contains one complete set of chromosomes. A gamete is a haploid cell produced through meiosis
32
Diploid cell
Cell that contains two sets of chromosomes. Each pair is considered to be homologous
33
Gregor Mendel
Responsible for discovering dominant and recessive traits. Identified this by creating a pure breed of purple and white flowered pea plant. Then he cross bread them and discovered the purple flour showed up 3 out of 4 times.
34
Dominant gene
This gene will always be displayed if present
35
Recessive gene
Will only be expressed if both parents have the gene
36
Phenotype
The physical characteristics/ description of a gene. Eg: blue eyes
37
Genotype
The genetic makeup of the gene. Eg: bb, Bb
38
Punnett Square
Easiest way to predict phenotype by using genotype from both parents in a Punnett square
39
Traits
Inherited characteristics
40
Alleles
Variations of genes. There can be dominant and recessive alleles
41
Heterozygous
Each allele is different, Eg, Hh, Bb
42
Homozygous
Both alleles are the same, eg:BB, bb
43
Co dominance
When both alleles are expressed equally
44
Incomplete dominance
When neither allele is expressed more than the other one
45
Chromosomal abnormalities
Offspring are born with an extra chromosome or part of a chromosome. This occurs when chromatids fail to separate properly during meiosis. Eg Down syndrome (extra chromosome no. 21), Klinefelter Chromosome (males receive an extra X chromosome)
46
Mutations
Occur when DNA is not copied correctly. Can occur n a varied scale depending on how much of the code is missing/ not copied properly
47
Sex linkage
Genes found on the chromosome also responsible for the determination of sex. Usually found on the X chromosome because it is longer and tends to carry more genes. Diseases can be carried on sex linked genes and passed on to offspring. The female is often the carrier due to it being on the X chromosome but isn't usually affected because it isn't a dominant gene. Eg: colour blindness, haemophilia.
48
Silent mutations
Do not affect the individual, when a single base on the DNA stand is changed
49
Missense mutations
Don't stop the gene from making a protein but the protein is a different one and may not function correctly. Eg. Sickle cell anaemia
50
Nonsense mutations
Causes the cell to stop reading the information. Protein created is not complete and can't function at all. Eg. Cystic fibrosis
51
Frame shift mutations
By insertion or deletion of a single base this causes all the information following to be jumbled up so that it cannot be read to make a protein. Result in severe genetic diseases
52
Down syndrome effects
Some degree of mental disability. Health issues are more likely to occur. Tendency to gain weight. Disruptive, hyperactive behaviours. Difficulty in social interactions. Depression, anxiety. Broader, flatter features. Most common form called trisomy 21 where individuals have 47 chromosomes instead of 46. Problem occurring at meiosis
53
Genetic modification
In GM organisms, genetic information is changed by inserting new genes. Manipulating genes and changing the genetic code. New genes are then copied to all the cells through mitosis. These modified cells will mature into a new strain of organism. This is used to create desirable traits in organisms
54
GM Canola
Canola creates edible oil. It has been modified to be resistant to herbicide so farmers can kill the weeds and have the canola unaffected. People are concerned the modified gene might be passed on to the weeds making them harder to control
55
GM rice
White rice lacks minerals and a vitamin A deficiency causes childhood blindness. GM Rice, golden rice, contains beta- carotene which the body converts to vitamin a. Genetically modified from daffodils, corn and bacteria.
56
Gene splicing
Bacteria have DNA in chromosomes and rings called plasmids. These plasmids can be cut using enzymes and have other desirable genes placed inside instead. This is called recombinant DNA technology. Eg can be used to create insulin for people with diabetes.
57
For GT
``` Elimination of disease, genetic disorder More efficient crops Medical advances Save lives Children for all Don't manipulate things, they were meant to be that way ```
58
Against GT
Designer babies is morally wrong Changing our food removing nutrients that are good Unethical and unnatural Cruel Have negative repercussions later on after changing everything Wrong to clone something, no inidividuals Lost biodiversity
59
Gene therapy
Has the potential to cure genetic diseases. The defective gene is replaced with a normal gene. Eg. In cystic fibrosis replacing normal CFTR genes into the lungs, so for it hasn't been successful
60
Gene technology
Gene technology is the term given to a range of activities concerned with understanding gene expression, taking advantage of natural genetic variation. Different techniques are used to improve characteristics.eg Selective breeding, AI
61
Genetic engineering
Broader term used for Manipulating the genetic code to promote favourable characteristics. Eg: high yield in crops, disease resistance, longevity
62
Cloning
Creating a genetically identical copy of an organism. Very controversial. Once characteristics are desirable in an animal or plant, it can be copied to ensure those characteristics are always present and already created in the next generation. Eg: dolly the sheep was the first cloned animal made in 1996.
63
Selective breeding
Manipulating breeding partners to promote characteristics. The conception, fertilisation and partuition is 'natural'

Science 2016 (7 decks)

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