2C Gene expression and GENETICS Flashcards
types of point mutation
• substitution
• deletion
• insertion
substitution mutation
type of point mutation; one base in a gene is substituted for another
deletion mutation
type of point mutation; a base is completely lost
insertion mutation
type of point mutation; an extra base is added into a gene
mutation
a permanent change in the DNA of an organism
gametes
haploid sex cells that fuse to form a new diploid cell (zygote) in sexual reproduction
chromosomal mutations
changes in the position of entire genes within a chromosome
whole-chromosome mutations
the loss of duplication of a whole chromosome
• e.g. down syndrome is caused by a whole-chromosome mutation at chromosome 21
mutagent
anything that increases the rate of mutation
e.g. X-rays, ionising radiation
variation
difference between organisms which may be the result of different genes or the environment they live in
phenotype
the physical traits, including biochemical characteristics, expressed as a result of the interactions of the genotype with the environment
genotype
the genetic make-up of an organism with respect to a particular feature
homologous pairs
matching pairs of chromosomes in an individual which both carry the same genes, although they may have different alleles
locus
the site of a gene on a chromosome
alleles
versions of a gene, variants
homozygote
an individual where both alleles coding for a particular characteristic are identical
heterozygote
an individual where the two alleles coding for a particular characteristic are different
dominant
a characteristic which is expressed in the phenotype whether the individual is homozygous or heterozygous for that allele
recessive
a characteristic which is only expressed when both alleles code for it; in other words, the individual is homozygous for the recessive trait
true breeding
a homozygous organism which will always produce the same offspring when crossed with another true-breeding organism for the same characteristic
monohybrid cross
a genetic cross where only one gene for one characteristic is considered
monohybrid cross
a genetic cross where only one gene for one characteristic is considered
codominance
in heterozygotes, where both alleles at a gene locus are fully expressed in the phenotype
sex-linked traits
characteristics which are inherited on the sex chromosomes
autosomes
chromosomes which carry information about the body but do not determine the sex of an individual
homogametic
an individual who produces gametes that contain only one type of sex chromosome - in humans this is the female
heterogametic
an individual who produces two types of gamete each containing different types of sex chromosome - in humans this is the male
transcription factors
proteins that bind to the DNA in the nucleus and affect the process of converting, or transcribing, DNA into RNA
epigenetics
the study of changes in gene expression (active versus inactive genes) that does not involve changes to the underlying DNA sequence but affects how cells read genes
sex-linked diseases
genetic diseases that result from a mutated gene carried on the sex chromosomes - ir human beings, on the X chromosome
red-green colour blondness
a sex-linked genetic condition which affects the ability to distinguish tones of red and green
haemophilia
a sex-linked genetic disease in which one of the factors needed for blood to clot is not made in the body
genetic screening
when whole populations are tested for a genetic disease
phenylketonuria PKU
a recessive genetic disorder where those affected lack the enzyme needed to digest the amino acid phenylalanine; the amino acid builds up in the blood and causes severe brain damage
parental screening
screening of an embryo or fetus before birth
amniocentesis
a type of prenatal screening which involves removing a sample of amniotic fluid at around 16 weeks of pregnancy, culturing the fetal cells found and analysing them for genetic diseases
chorionic villus sampling
a type of prenatal screening where a small sample of embryonic tissue is taken from the developing placenta and the cells tested for genetic diseases
preimplantation
genetic diagnosis testing the cells of an embryo produced by IVF to check for genetic diseases before it is implanted into the uterus of the mother
PKU
phenylketonuria
At what point during the pregnancy are amniocenteses performed?
at about the 16th week of pregnancy
when during pregnancy is a chorionic villus sampling performed?
at about 8-10 week of pregnancy
why do most mutations have no observable effects on the organism?
- the mutations occur in part of the non-coding DNA which does not affect the way the genetic code is read
- the code is degenerate, and one small change in the code may not alter the amino acid coded for
what are the two types of chromosomes found in cells?
autosomes and sex chromosomes
