Human genetics: L18 Flashcards
what is a phenotype?
physical characteristics:
observable properties of an organism produced by the genotype and environmental influences
example of a phenotype for someone with down’s syndrome
- sloping forehead
- protruding tongue
- short limbs
- flattened nose
- almond eyes
- congenital eye, ear and heart defects
other examples of phenotype
- hair colour
- executive function abilities
- short/tall
- lung capacity
- psychiatric condition
- skin tone
genetic structures
- human body has … cells
- there is a … inside each cell (except red blood)
- each nucleus has … chromosomes
- one chromosome from every pair is from ….
- chromosomes are filled with ….
- … are segments of DNA that contain …
- 100 trillion
- nucleus
- 46
- each parent
- tightly coiled strands of DNA
- genes, contain instructions to make proteins = building blocks of life
- define Gametes
- each contain how many chromosomes?
- X/Y =
- X/X =
sex cells - sperm from male, ova from female
- 23
- X/Y = male
- X/X = female
each chromosome pair.. (2)
- carries genes of the same type
- match in size and function they serve
chromosome
- information is arranged in …
- chromosomes are made up of … which is made up of ….
- chromosomes are only visible during…
- linear sequence
- chromatin. Chromatin constitutes nucleic acids (DNA & RNA) & proteins
- cell division processes, called mitosis and meiosis
define karyotype
chromosomal content of a cell
what are the autosomes?
non sex chromosomes (numbered 1-22)
variations in karyotype:
- 46, XY
- 46, XX
- 47, XY + 21
- 47, XX + 21
- 45, X
- 47, XXY
- Male
- Female
- male down’s syndrome
- female down’s syndrome
- Turner’s syndrome
- Klinefelter’s syndrome
what is Klinefelter’s syndrome?
- physical development
- language development
- social development
- weak muscles/reduced strength
- 25-85% have language difficulties
- XXY males tend to be more quiet and undemanding than XY males
which DNA always bind together? 2 pairs
- adenine and
- guanine and
- thymine
2. cytosine
sequence of DNA is described by the order of the bases in a what direction?
5’ to 3’ direction
humans have … bases
3.3 x 109
what is the locus used to describe
a sequence of DNA situated on a specific region on a chromosome
DNA is…
a double-stranded structure consisting of 2 nucleotides held together by hydrogen bonds between the bases in opposing (anti-parallel) strands
DNA molecules are organised into stretches of sequence called…
genes
Richard Dawkins described genes as
any portion of chromosomal material that potentially lasts for enough generations to serve as a unit of natural selection
- each gene has one or more …
- each gene can … with another gene
- each gene can … into different forms
- genes are expressed at …
- a gene can only influence human development when…
- for DNA to impart information it must be …
- specific effects upon the phenotype of the organism
- recombine
- mutate
- different time points in life
- its turned on and expressed
- transcribed
The strand of DNA acts as a … for the synthesis of ….
- template
2. ribonucleic acid (RNA)
RNA forms stable structures by …
base-pairing (like DNA)
DNA information can be … to RNA for …
- copied
2. transcription and translation and carried to other areas of the cell to create proteins
what do messenger RNA do?
carry instructions specifying sequences of amino acids
- groups of … of mRNA …
- > these groups are called …
- > how many potential codons & amino acids?
- 3 bases
- serially code for each amino acid
- > codons
- > 64 codons, 20 different amino acids
Protein types
- enzymes
- haemoglobin
- insulin
- collagen
- keratin
- histones
- actin and myosin
- immunoglobulins
what are alleles?
- 1/3 of human genes have two or more different forms called alleles
- one or two or more forms (or variations) of a gene
the alleles of a give gene ….
influence the same trait or characteristic e.g. eye colour
-> different allele forms result in different eye colours
Geneticists track the sequence of one strand of DNA complex because…
the other is determined by the complementarity rule
- homozygous alleles example
2. heterozygous example
- F: AAG T TGG
M: ATC T ACG - F: AAG A TGG
M: ATC T AGC
(look at middle letter)
- dominant allele is …
2. recessive allele is expressed when…
- expressed if present
2. expressed if dominant is absent
What is polygenic inheritance?
- when traits are governed by more than one gene
What is mitosis?
- process of cell replication and division in which the cell separates the chromosomes in the cell nucleus into 2 identical sets, 2 separate nuclei
= genetically identical
- What is meiosis necessary for?
- what does it produce?
- what happens?
- sexual reproduction
- gametes
- DNA replicated, recombined and the cell divides twice
- Mitosis = each daughter cell with … chromosomes
2. meiosis = each daughter cell with … chromosomes
- 46
2. 23
- Mitosis = how many daughter cells
2. meiosis = how many daughter cells
- 2
2. initially 2 -> split into 4
mutation definition
-> source of ?
the process of change in the sequence of DNA
-> genetic variation and basis for natural selection
How do mutations occur?
- spontaneously
- or induced by external factors e.g. exposure to chemicals
4 main types of mutations
- base substitutions
- deletions of DNA
- insertions of DNA
- whole or partial chromosomal abnormalities
How does Turner’s syndrome affect development?
- intellectual
- physical
- sexual
- intellectual disability
- movement control problems
- 99% present as female
