definitions Flashcards

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1
Q

Asexual reproduction

A

Production of offspring without joining of gametes

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2
Q

sexual reproduction

A

Production of offspring by joining gametes

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3
Q

gamete

A

sex cells (sperm and ova)

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4
Q

gonad

A

organs that produce gametes (testes & ovaries)

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5
Q

menstruation

A

Shedding of uterine lining (endometrium) at the start of the menstrual cycle

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6
Q

ovulation

A

release of an ovum from an ovary, normally occurs in the middle of the menstrual cycle

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7
Q

fertilisation

A

Union of ovum and sperm (to form a zygote)

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8
Q

implantation

A

Sinking into the endometrium of an embryo

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9
Q

zygote

A

Fertilised ovum

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10
Q

embryo

A

Early stage of development of a foetus

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11
Q

karyotype

A

An image depicting the full complement of an individual’s chromosomes

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12
Q

gene

A

regions of DNA that code for the production of specific traits.

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13
Q

chromsomes

A

long thin strands of DNA that are located in the nucleus of cells. They contain genes.

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14
Q

homologous

A

Matching (eg homologous chromosomes are matching chromosomes)

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15
Q

autosome

A

chromosomes (other than sex chromosomes) that do not code for gender (eg 1 to 22 in humans)

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16
Q

sex chromosome

A

chromosomes that do code for gender (23rd pair in humans)

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17
Q

maternal chromosome

A

from mother (in ovum)

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18
Q

paternal chromosome

A

from father (in sperm)

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19
Q

DNA

A

Deoxyribonucleic Acid – a double helix shaped chemical that makes up chromosomes

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20
Q

nucleotide

A

building block of DNA

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21
Q

nitrogenous base

A

part of nucleotide – DNA has 4 – Adenine, Thymine, Cytosine, Guanine

22
Q

DNA replication

A

Copying of DNA to produce a chromosome that consists of 2 chromatids, occurs before cell division

23
Q

chromatid

A

one strand of a replicated chromosome

24
Q

centromere

A

part of a duplicated chromosome that holds the chromatids together

25
Q

somatic cells

A

body cell

26
Q

diploid

A

full number of chromosomes (eg in humans 46 as in body/somatic cells)

27
Q

haploid

A

Half number of chromosomes (eg in humans 23 as in gametes)

28
Q

mitosis

A

nuclear division to produce daughter cells that are identical (for growth and repair)

29
Q

meiosis

A

nuclear division to produce gametes (reduction division – daughter cells have half the number of chromosomes)

30
Q

cytokinesis

A

cell division – occurs after nuclear division

31
Q

inheritance

A

passing of characteristics from one generation to another

32
Q

locus

A

possession of gene in a chromosome

33
Q

alleles

A

alternative forms of a gene (eye colour)

34
Q

dominant allele

A

the trait expressed when heterozygous

35
Q

recessive allele

A

the trait that is hidden when heterozygous

36
Q

genotype

A

the combination of alleles present using letters

37
Q

phenotype

A

the visible affect of the allele combination

38
Q

homozygous

A

where both identical alleles are present

39
Q

heterozygous

A

where both alleles are different

40
Q

pedigree

A

A diagrammatic representation of the inheritance of a trait in a family

41
Q

punnet square

A

Grid used to summarise predicted allele combinations in offspring

42
Q

complete dominance (inheritance)

A

Inheritance pattern where the dominant allele completely dominates the recessive allele (gives 2 phenotypes)

43
Q

co-dominance (inheritance)

A

Inheritance pattern where different alleles are equally expressed (could produce 3 phenotypes)

44
Q

multiple allele (inheritance)

A

Inheritance pattern where there are more than 2 alleles for a gene (eg ABO blood type)

45
Q

sex (X) linked (inheritance)

A

Where gene studied is located on the X sex chromosome (not on an autosome)

46
Q

mutations

A

Changes to the DNA sequence in genes and chromosomes

47
Q

mutagens

A

Factos that cause changes in DNA. radiation (e.g. ultraviolet radiation, nuclear radiation and X-rays) and some chemical substances (e.g. pesticides, hair dyes, food preservatives and substances in cigarette smoke).

48
Q

gene mutations

A

Small scale changes to the DNA base sequences within genes.

49
Q

chromosome mutations

A

Larger scale mutations involving whole extra or missing chromosomes (aneuploidy), or large sections of chromosomes being translocated or deleted.

50
Q

traits

A

characteristics