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Medical Science > Cell Biology and Genetics > Flashcards

Cell Biology and Genetics Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
0
Q

Define aneuploidy

A

The condition in which the chromosome number of the cell is not an exact multiple of e haploid number

Monosomies and trisomies are examples of aneuploidy

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1
Q

Define allele

A

One of series of alternative versions of a gene or DNA sequence at a given locus

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2
Q

Define antisense

A

A piece of nucleic acid, typically created in the lab, which has a sequence exactly opposite to an mRNA molecule made by the body

Antisense can bind tightly to its mirror image mRNA, preventing a particular protein from being made

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3
Q

Define autosomal dominant

A

A trait or disease that is produced when only one copy of a polymorphism or mutation is present on an autosome

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4
Q

Define autosomal recessive

A

A trait or disease that is produced when two copies of a polymorphism or mutation are present on an autosome

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5
Q

Define autosome

A

Any chromosomes other than sex chromosomes

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6
Q

Define cell

A

The cell is the basic unit of life

If it is to survive, each cell must maintain an internal environment that supports its essential biochemical reactions, despite changes in the external environment

Therefore, a selectively permeable plasma membrane surrounding a concentrated aqueous solution of chemicals is a feature in all cells

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7
Q

Define a clone

A

A member of a group of cells that all carry the same genetic information, and which are derived from a single ancestor by repeated mitosis

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8
Q

Define compound heterozygote

A

An individual with two different mutant alleles at the same locus

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9
Q

Define consultand

A

An individual seeking, or referred for, genetic counselling

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10
Q

Define exon

A

Region of a gene containing DNA that codes for a protein

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11
Q

Define gamete

A

The reproductive cell formed by meiosis, containing half the normal chromosome number

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12
Q

Define genome

A

This is the entire genetic complement of a cell

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13
Q

Define genotype

A

This is the genetic constitution of an individual, and it is also used to refer to the alleles present at one locus

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14
Q

Define heritability

A

The degree to which a characteristic is determined by our genes

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15
Q

Define heterozygote

A

This is an individual or genotype with two different alleles at a given locus on a pair of homologous chromosomes

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16
Q

Define holoenzyme

A

The complete enzyme including all its subunits and cofactors

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17
Q

Define homozygote

A

An individual or genotype with identical alleles at a given locus on a pair of homologous chromosomes

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18
Q

Define hormone

A

A molecule produced by an endocrine cell, which is released into the blood stream and acts on specific receptors to elicit its effect

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19
Q

Define host

A

The organism used to propagate a recombinant DNA molecule

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20
Q

Define an insert

A

The fragment of foreign DNA cloned into a particular vector

21
Q

Define intron

A

A section of a gene that does not contain any instructions for making a protein

22
Q

Define karyotype

A

This is the chromosome complement of a cell

In a standard karyotype, the chromosomes are conventionally arranged in order depending upon size

Chromosomes are distinguished individually by their size, centromere position and banding pattern

The normal human karyotype is 46, XY (male) or 46, XX (female)

23
Q

Define library

A

A collection of cloned DNA fragments which, taken together, represent the entire genome of a specific organism

Using traditional techniques they allow the isolation and study of individual genes

24
Q

Define ligand

A

A molecule, such as a hormone or neurotransmitter, which binds to the receptor, and is termed the first messenger

25
Q

Define locus

A

The position of a gene on a chromosome

26
Q

Define microarray

A

A large set of cloned nucleic acid molecules or proteins spotted onto a solid matrix, usually a microscope slide, and used to profile gene and protein expression in cells and tissues

27
Q

Define monosomy

A

A chromosome constitution in which one member of a chromosome pair is missing

28
Q

Define multifactorial disorders

A

A term used to describe disorders in which both environmental and genetic factors are important

29
Q

Define mutation

A

A permanent heritable change in a sequence of DNA

30
Q

Define neurotransmitter

A

A molecule that is used to transmit nerve impulses across a synapse

31
Q

Define an operon

A

A prokaryotic locus, consisting of two or more genes that are transcribed as a unit and are expressed in a coordinated manner

32
Q

Define organism

A

An organism is a system capable of self-replication and self-repair, which may be unicellular or multicellular

Unicellular organisms consist of a solitary cell able independently to perform all the functions of life

Multicellular organisms contain several different cell types that are specialised to perform specific functions

33
Q

What is a pedigree chart?

A

They are used to illustrate inheritance

34
Q

Define penetrance

A

The proportion of individuals with a specific genotype that show the expected phenotype under defined environmental conditions

The term is usually used in association with dominant disorders

35
Q

Define phenocopy

A

The alteration of the phenotype by environmental factors during development to produce a phenotype that is characteristically produced by a specific gene

36
Q

Define phenotype

A

The observed biochemical, physiological or morphological characteristics of an individual that are determined by the genotype and the environment in which it is expressed

37
Q

What is a plasmid?

A

Autonomously replicating, extrachromosomal circular DNA molecules

Often exploited in the laboratory as a vector for gene cloning

38
Q

Define pleiotrophy

A

The phenomenon in which a gene is responsible for several distinct and apparently unrelated phenotypic effects, which may concern the organ system involved and the signs and symptoms that occur

39
Q

Define ploidy

A

This refers to the number of complete sets of chromosomes in a cell.

A haploid cell contains a single set of chromosomes

A diploid cell contains two copies of each chromosome

A polyploid cell contains more than two sets of each chromosome

40
Q

What is polygenic inheritance?

A

This is a term used to describe the inheritance of traits that are influenced by many genes at different loci

41
Q

What is polymorphism?

A

Polymorphism is the occurrence in a population of two or more alternative genotypes, each at frequency greater than that which could be maintained by recurrent mutation alone

A locus is arbitrarily considered to be polymorphic if the rarer allele has a frequency of at least 0.01

Any allele rarer than this is a ‘rare variant’

42
Q

Define proband

A

The first person in a pedigree to be clinically identified as having a disease in question

43
Q

Define a probe

A

A probe is a radioactively or fluorescently labelled piece of single-stranded DNA of defined sequence

44
Q

Define recombinant DNA

A

A molecule of DNA created ‘in vitro’ that contains elements of more than one original sequence, e.g. vector and insert

45
Q

What is rolling circle replication?

A

A process of nucleic acid replication that can rapidly synthesise multiple copies of circular molecules of DNA such as bacterial chromosomes and plasmids

46
Q

Define translocation

A

The transfer of one segment of a chromosome to another

47
Q

Define trisomy

A

The state of having three representatives of a given chromosome instead of the usual pair

(E.g. As in trisomy 21 - Down syndrome)

48
Q

What is variable expressivity?

A

This occurs when a genetic lesion produces a range of phenotypes:

  • e.g. tuberous sclerosis can be asymptotic with harmless kidney cysts, but in the next generation it may be fatal, owing to the development of brain malformations
49
Q

What is vector?

A

A DNA molecule capable of replicating within a particular host, into which foreign DNA may be inserted

50
Q

Define X-linked dominant

A

A trait (or a disease) that is produced when only one copy of a polymorphism or mutation is present on an X chromosome

This means that both males and females can display the trait or disorder, by only having one copy of the gene

51
Q

Define X-linked recessive

A

A trait or disease that is produced when a polymorphism or mutation in a gene on the X chromosome causes the phenotype to be expressed

Medical Science (8 decks)

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