B5.1 - Inheritance Flashcards
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Define a phenotype
The appearance of an organism
The visible characteristics of an organism which occur as a result of its genes.
Define variation
The differences within a species
What are the two types of variation, explain
Genetic variation (genetic material inherited from parents) Environmental variation (variation caused by your environment - ie. sunlight, hair length - if you cut it or not)
Are most features caused by a single gene or multiple?
Usually multiple genes
What is discontinuous variation?
how to show graphically
- variation that can only result in discrete values (one)
- ONLY GENETIC
- ie. blood group, gender, eye colour
- bar chart
What is continuous variation?
how to show graphically
- variation that can take any value within a range
- genetic + environmental
- ie. length of fur, skin colour, leaf surface area
- histogram (single line)
Define a clone
An organism that is genetically identical to its parent
What is asexual reproduction?
When a single organism reproduces itself (by mitosis), and produces new daughter cells genetically identical to itself
What is different between the offspring in sexual and asexual reproduction and why?
Asexual reproduction has the exact same genetic material as the parent, whereas sexual is not identical to parents as the offspring takes genetic information from both parents
Define gametes
Sex cells (ie. sperm cell, egg cell)
What happens during fertilisation?
Two gamete fuse together
Advantages/ disadvantages of asexual reproduction?
Adv - if parent well adapted, offspring has identical characteristics
- one parent needed (reproduction faster = more offspring)
Dis - adapted to one habitat (may all die out if abiotic factors change)
- lack of variation, one disease can wipe our all
Adv/Dis of sexual reproduction?
Adv -
- produces genetic variation in the offspring
- the species can adapt to new environments due to variation, which gives them a survival advantage
- a disease is less likely to affect all the individuals in a population
Dis
- reproduction needs two parents (slower = less offspring)
- time and energy are needed to find a mate
What are diploid cells in humans?
how many chromosomes
Normal body cells (46 chromosomes)
What are haploid cells in humans?
How many chromosomes
Sex cells (ova/sperm cells) - 23
What is formed when two gamete cells join together?
Diploid cell or ‘zygote’
What process causes the zygote to divide many times to produce a new organism?
Mitosis
Define genome
All the genetic material within an organism
How is meiosis used in the body?
To produce gametes/ sex cells
What kind of cells are present at the start of meiosis and what are present at the end?
ONE diploid parent cell at start
FOUR haploid daughter cells at end
Where does meiosis occur in females, and males?
And what is produced
Females - ovaries (makes ova cells)
Male - testes (sperm cells)
Draw out how meiosis works + label diagram
+ recombination
Define alleles
Different forms of a gene
What’s the different between dominant and recessive alleles?
Dominant - will always show up
Rr or RR
Recessive - only show up if there are two of them
only rr
Define a genotype
The combination of alleles present in an organism
The alleles that an organism has for a particular characteristic
What does the genotype of a dominant homozygous individual look like/ a recessive homozygous/ and a heterozygous
GG/ gg/ Gg
Give 3 examples of dominant characteristics
Give 3 examples of recessive characteristics
DOM - free ear lobes
- brown eyes
- dark, wavy hair
REC - joined ear lobes
- blue eyes
- straight, blonde hair
Who figured out the basic laws of inheritance of characteristics?
(And how)
Mendel (was a Catholic monk)
Carried out experiments on pea plants
In the genetic cross between a man who is heterozygous for the Huntington’s allele and a woman who is homozygous recessive for the Huntington’s allele (h).
State the proportion of
(a) homozygotes dominant offspring
(b) heterozygous offspring
(c) homozygotes recessive offspring
(a) 0%
(b) 50%
(c) 50%
(A) What does a female’s 23rd pair of chromosomes look like?
(B) what does a male’s 23rd pair of chromosomes look like?
(A) XX
(B) XY
What ‘thing’ determines the sex of a baby?
Whether the sperm cell which fertilises the ova cell contains an X or a Y chromosome on the 23rd place.
As it is a HAPLOID cell (has 23 chromosomes only)
What is a mutation?
A change in which the sequence of DNA bases is altered (may or may not result in a change to the phenotype)
Where do variants arise from in a population?
From mutations (change in DNA)
Are all mutations harmful?
Not all, most will not even affect phenotype.
However the ones that do affect phenotype are usually harmful
Give examples of harmful mutations
- cancer (grow + divide uncontrollably)
- production of abnormal protein channels that don’t function correctly (e.g. cystic fibrosis)
- different shaped protein molecules made (sickle cell anaemia)
Give an example of a helpful mutation, and a neutral mutation
Help - antibiotic resistant bacteria
Neutral - being able to roll your tongue
Give an example of what could happen if a mutation occurs within. A gene
- dna bases change/add/deleted
- change sequence of bases (mRNA Produced is different)
- animo acids assembled incorrectly
- wrong protein forms/ fold incorrectly/ active site does not wok
- cannot bind to substrate/ catalyse reaction
What happens if a mutation occurs within a non-coding region of DNA?
Gene may not be transcribed into mRNA (protein gene codes from not produced)
What did Mendel discover and how, and when?
1) characteristics in plants determined by hereditary units
2) hereditary units passed on from both parents (one unit from each)
3) hereditary units dominant/ recessive
We now call them genes
1866
What did Miescher discover and when?
- acidic substance in nucleus of cell (DNA)
1869
Who discovered that genes are made of DNA?
Avery, transferred DNA between bacteria (passed trait to cause disease to offspring)
1950
Who first found the helical structure of DNA and when?
Wilkins and Franklin (X-rayed DNA crystals)
1952
What did Watson and crick do?
Published description of DNA (complementary base pairings + double helix)
1953
Who is dolly the sheep and why is she special?
In 1996, was first cloned animal from adult cell
What happened in 2003?
Scientists sequenced 24,000 genes (complete set of genes in human body)
what influences the development of the phenotype of an organism?
the genome and its interaction with the environment
how could genetic variants affect the phenotypes in coding DNA (protein)
- mutations affecting protein structure
- affect active site of enzymes
how could genetic variants affect the phenotypes in non-coding DNA?(expression of genes)
- stopping transcription of DNA
What is the mnemonic to remember the order of scientists?
Mixed martial arts can foster world wide carnage
M endel M iescher A very C hargaff F rankil W ilkins W atson C rick
Mnemonic to remember order of discovery of DNA?
DR nuclei goes pants seeing penguins
DR - dominant/recessive N - nuclei (acidic) G - genes (bacteria transfer) P - pairings (equal AT and GC) S - structure (x ray) P - publish (stealing work of Franklin)
what did chargaff do?
DNA contains equal amounts of adenine and thymine
and cytosine and guanine
Is pain phenotype or genotype
Phenotype - according to multiple choice 2018
If you get rid of the X chromosome in male sperm , how does that effect offsprings
- only male offsprings can be produced
Stages of meiosis
- Thechromosomes are copied
- The chromosomes line up upon the midline of the cell in pairs (one from the father, one from the mother)
- Spindle fibres form
- Spindle fibles contract towards the oppostive poles
- One member of each pair is pulled to opposite ends of the cell - sections of DNA are often swapped at this stage (crossing over & recombination).
- The cell divides in two form two separate cells
Stage 2:
- The chromosomes line up upon the midline of each new cell
- Spindle fibres form
- Spindle fibles contract towards the oppostive poles
- The chromosomes are pulled in half - a single copy of each chromosome goes to the opposite end of the cell
- Each cell divides in two. This results infour haploid (n), genetically diffenrentcells.
Compare mitosis and meiosis
Mitosis
- The cell divides once
- Two cells produced
- Same number of chromosomes as parent cell
- Used for growth & repair
- Happens in all parts of the body
- Daugther cells genetically identical to parent cell
Meiosis
- The cell divides twice
- Four cells produced
- Half the number of chromosomes as parent cell
- Used to produce gametes
- Happens in the gonads only (testes/ovaries)
- Daugther cells genetically unique cells to parent cell
