Inheritance Flashcards
Which of these statements is true
Genes make up chromosomes.
Chromosomes make up genes.
Genes make up chromosomes
Different genes control the development of different _______________
Characteristics
What is a gene
A section of DNA which codes for 1 characteristic
Describe the structure of a DNA molecule
Double helix
How can you work out the sequence if the bases on one strand by looking at the sequence on the other
It is always the opposite
‘A’ goes with ___
And ‘C’ goes with ___
A –> T
C –> G
___ bases code for one amino acid
3
What is a mutation
A random change in the DNA
What is the genotype
Your complete genetic identity… the allele pair (You may be {B b} or {B B}
What is the phenotype
The observable characteristics (Brown eyes)
Inside every cell in our bodies there is ___________ information. The information is carried in __________
Genetic information
Genes
Some characteristics are not present due to genes but by the ______________
Environment
Some genes can be controlled by both genes and the environment e.g…
For example height and weight
List 2 examples of continuous variation in humans
Height
Weight
List 3 types of discontinuous variation in humans
Eye colour
Hair colour
Blood type
List 3 causes of variation
Genes
Environment
Mutation
What are the 4 stages in mitosis in order
Prophase
Metaphase
Anaphase
Telophase
Describe the main stages in the division of cell?
The dividing cell copies each chromosome before it divides. Therefore every cell has one copy of every chromosome. 2 chromatids make up each chromosome. These attach to a structure called a spindle. The spindles then shorten and pull the chromatids of each chromosome to the polar ends. 2 new nuclei form, both with a copy of each chromosome
Why does the chromosome need to make an EXACT copy of itself before the cell can divide
Otherwise both cells will not receive all the genes
When a cell is about to divide, it first makes an exact copy of each DNA molecule - this is called ______________
Replication
How does a mutation occur
During replication, if a mistake is made.
Name the 4 ways a mutation can occur
Duplication
Deletion
Substitution
Inversion
Some _____________ occur in body cells and will only affect that particular cell. If the ___________ is not lethal and the cell containing the mutation divides, then a group of cells will have that ___________. When the organism dies, the ___________ is ______. Only a __________ in the __________ can be passed on to the next generation
Mutations Mutation Mutation Mutation Lost Mutation Gametes
What are the 4 effects of mutations
Lethal
Harmful
Silent
Beneficial
New alleles originate by __________
Mutation
Only mutations in ________ can be inherited
Gametes
New alleles introduce genetic ____________
Variation
Causes of gene mutation
Ionising radiation Viruses and microorganisms Environmental poisons Tobacco Alcohol and diet
What is an allele
A different version of a gene
What does homozygous mean
The same alleles
What does heterozygous mean
Different alleles
Is it possible for a recessive allele to be passed on
Yes… both alleles must be present for that characteritic to be shown
What is codominance
When the characteristics are mixed. The genotype is heterozygous. Neither allele is dominant or recessive to the other one. You get a mix of the 2 characteristics.
Male genotype
XY
Female genotype
XX
DNA replication. The DNA must first ___________. An ___________ called helicase helps. Each strand acts a template. The DNA ________________ match up to the bases on each strand. C matches with ____ and A matches with ___. Another enzyme, DNA polymerase, joins the ________________ together along the new strand. Another enzyme, ligase, helps stick them together
Unwind Enzyme Nucleotides G T Nucleotides
Chromosomes are located in a __________ which is surrounded by ______________
Nucleus
Cytoplasm
Each ___________ consists of a row of genes
Chromosome
Differences between organisms of the same species are known as ______________
Variation
Body cells contain 46 chromosomes. Gametes contain half this number and are therefore said to be ___________
Haploid
Number of chromsomes: Ovum
23
Number of chromsomes: Sperm
23
Number of chromsomes: Zygote
46
Explain how mitosis results in cells with identical sets of genetic information
Because before the cells divide the DNA replicates itself. The chromosome then splits in 2 before the cell splits sp both cells have an identicle chromosome
First the DNA ___________
Then, the DNA copies itself before it coils up and forms _______________
The _______________ then line up in the centre of the cell
Next, the arms of each ________________ are pulled apart
New _____________ form around the cell nuclei
The cell divides.
This process is known as ___________.
Uncoils Chromosomes Chromosomes Chromosome Membranes Mitosis
Why do gametes have half the usual number of chromosomes
For variation, when fertilisation occurs it goes back to the usual number
How does gamete formation lead to genetic variation
The child isn’t identical to one parent. It’s a mix of both.
New forms of genes arise from changes known as ___________________ in the existing genes. These occur naturally and are important for producing ______________
Mutations
Variation
Name something which increases the chance of a mutation occuring
Exposure to ionising radiation
Exposure to chemicals known as mutagenes
What has to happen for a mutation to be passed on
The mutation has to occur in the sex cells
