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Biology Glossary for IGCSE > M: Inheritance > Flashcards

M: Inheritance Flashcards

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1
Q

Allele

A

One form of a gene. E.g. the eye-colour gene has an allele for blue and another for brown (and several other variations of these!)

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2
Q

Artificial selection

A

The selection by humans of individual plants or animals for breeding in order to enhance a desired characteristic.

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3
Q

Base pairing

A

Complementary pairing of bases in DNA: Adenine always pairs with Thymine and Guanine pairs with Cytosine.

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4
Q

Carrier

A

A person who carries one recessive allele for a particular disease, but doesn’t have symptoms.

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5
Q

Chromatid

A

One of two daughter strands of a replicated chromosome.

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6
Q

Chromosomes

A

Red shaped structures found in the nucleus of cells, made of DNA, each carrying many genes.

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7
Q

Clone

A

An organism which is genetically identical to another. Clones can arise naturally (asexual reproduction or identical twins), or be produced artificially.

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8
Q

Codominance

A

Situation in which two alleles of a gene contribute to the phenotype of a heterozygote. E.g. blood group genes A & B are codominant.

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9
Q

Codon

A

Group of three bases, e.g. ‘CGA’ in DNA (or RNA) which codes for one amino-acid.

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10
Q

Continuous variation

A

Type of variation in which values are spread across a complete range, often with a bell-curve distribution. Quantitative variation.

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11
Q

Discontinuous variation

A

Type of variation in which values fall into distinct classes, with no continuous spread of data. Qualitative variation.

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12
Q

Diploid

A

Containing two sets of chromosomes (one set of 23 from each parent, so 46 in all) All human cells except gametes are diploid.

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13
Q

DNA

A

The material inside the nucleus of cells which carries genetic information. DNA stands for Deoxyribonucleic Acid.

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14
Q

Dominant

A

An allele that always expresses itself if present, whether it is partnered by a recessive allele or by another like itself.

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15
Q

Double helix

A

The shape of the DNA molecule: like a twisted rope ladder, with a sugar-phosphate ‘rope’ down each side, and base-pairs for the ‘rungs’.

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16
Q

Embryo transplanting

A

Genetic engineering technique in which an embryo is created from the egg of one animal fused with DNA from another animal, and then implanted into the womb of a surrogate mother.

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17
Q

Fermenter

A

Large temperature-controlled tank, in which huge numbers of bacteria can be grown quickly, e.g. to produce engineered insulin.

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18
Q

Fossil

A

Hardened remains or impression of an organism that existed in the geological past.

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19
Q

Gene

A

Unit of genetic material that is inherited from our parents. A gene is a section of DNA which codes for a protein.

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20
Q

Gene pool

A

The sum total of all the gene variations in a population or species.

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21
Q

Gene therapy

A

Treating or preventing disease by introducing or replacing specific genes inside human cells.

22
Q

Genetic disease

A

Disease which children can inherit from their parent/s as a result of abnormalities in their genes. E.g. cystic fibrosis.

23
Q

Genetic engineering

A

Manipulation of an organism’s DNA to change the proteins it produces. Involves transferring a gene using restriction enzymes and a vector.

24
Q

Genotype

A

The genetic make-up of an individual organism

25
Q

Haploid

A

Having one set of chromosomes (23, in humans). In humans and plants, only the gametes are haploid, other cells are diploid.

26
Q

Heterozygous

A

Having different alleles for a particular characteristic

27
Q

Homozygous

A

Having the same alleles for a particular characteristic

28
Q

Hybrid vigour

A

The increased strength and size of a hybrid (an offspring produced as a result of breeding two genetically different organisms) compared to that of the parents.

29
Q

Ligase

A

Enzyme used to re-join pieces of DNA in genetic engineering

30
Q

Meiosis

A

Type of cell division which forms four genetically-different daughter cells (gametes), which are haploid.

31
Q

Mitosis

A

A type of cell division which produces two daughter cells, both genetically identical to the parent.

32
Q

Mutagen

A

A chemical (e.g. mustard gas) which increases the rate if mutation

33
Q

Mutation

A

A rare error in DNA replication causing a change in an organism’s genetic information. Mutations are random events, but the chances can be increase by ionising radiation or chemical mutagens. Most mutations are harmful or neutral, but any beneficial mutation will tend to increase, by natural selection.

34
Q

Natural selection

A

The natural process whereby the best-adapted individuals survive longer and have more offspring, thereby spreading their characteristics through a population. ‘Survival of the fittest.’

35
Q

Nitrogenous bases

A

The chemical ‘letters’ that make up the language of DNA: Adenine (A), Cytosine (C), Guanine (G) and Thymine (T)

36
Q

Nucleotide

A

Monomer (unit) of DNA; built from a nitrogenous base, a 5-carbon (pentose) sugar and phosphate group

37
Q

Pentose sugar

A

A 5-carbon sugar; in DNA the sugar is deoxyribose, ribose in RNA

38
Q

Phenotype

A

Observable characteristics of an organism - the visible expression of its genetic make-up

39
Q

Plasmid

A

Small loop of DNA, found in bacteria, which can be used in genetic engineering as a vector to carry genes from one cell to another.

40
Q

Protein synthesis

A

Manufacturing of proteins; occurs at ribosomes in the cytoplasm, using an RNA code copied from the DNA in the nucleus.

41
Q

Purebread

A

Old word for homozygous, having the same alleles for a characteristic. Purebred organisms always breed true to type.

42
Q

Recessive

A

Allele of a gene for a particular characteristic which is masked or suppressed in the presence of the dominant variant. A recessive allele’s character is only seen when it is paired with another recessive allele.

43
Q

Recombinant

A

DNA which contains an artificially added gene, or has been exchanged between chromosomes during meiosis.

44
Q

Replication

A

Production of an identical copy. DNA replication involves the two strands ‘unzipping’ and new nucleotides being added to each half by base-pairing: this ensures each copy is identical to the original.

45
Q

Restriction enzyme

A

Enzyme which cuts DNA at a specific sequence of bases (e.g. TTCGAA), used in genetic engineering.

46
Q

RNA

A

(RiboNucleic Acid) - used to convert the genetic information stored in DNA into proteins

47
Q

Sex chromosomes

A

The pair of chromosomes that determine sex. Females have two X chromosomes and males have X & Y

48
Q

Spindle fibres

A

Fibres produced during cell division. They contract to drag chromatids to the poles of the cell.

49
Q

Triplet code

A

The genetic code made by a triplet of bases in the DNA chains: AAA; GCT;CAT etc.

50
Q

Variation

A

Difference between individuals. Variations can be caused by genetic differences or the environment, or both.

51
Q

Vector

A

A means of transferring genes during genetic engineering. Both viruses and plasmids can be used as vectors.

Biology Glossary for IGCSE (13 decks)

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