Inheritance Flashcards
What is a gene?
A section of DNA that codes for a specific protein (eg melanin or keratin) to produce a particular characteristic.
What is a chromosome?
A long DNA molecule that is found in a cell nucleus, and has many genes in it. It has stabilising proteins.
How is the structure of DNA composed?
Two parallel strands called backbones, which are made of sugar (deoxyribose) and phosphate. They are joined together in regular intervals by pairs of bases (A, T, C and G). The molecule is twisted, forming a double helix.
What are nucleotides made of?
- Bases (A, T, C and G)
- Sugar (Deoxyribose)
- Phosphate
What are the four bases?
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
Which bases always pair up?
- Adenine and Thymine
- Cytosine and Guanine
Why is DNA shaped as a double helix?
It is more stable
What do genes do?
Provide instructions for the cell to make proteins.
Which is important for controlling the proteins made, the bases, or their sequence?
The sequence of the bases
What is a mutation in DNA?
When something goes wrong when copying the DNA to make proteins.
OR
A change in the DNA sequence
What are some common mutations in DNA?
- THE CAT ATE THE FAT RAT (normal)
- THE CAT ATE THE FAT TAR
- THE CAT ATE THE FAT BAT
- THE CAT TET HEF ATR AT
How many chromosomes do human body cells contain?
46
How many pairs of chromosomes do human body cells contain?
23 pairs, one from your mother, one from your father.
How many copies of each gene do you have, and do these copies have to be the same?
2 copies of each gene, and no they must not be the same.
How many chromosomes do human gametes contain?
23, and are haploid
What are the sex chromosomes in humans called?
X and Y
(XX is female, XY is male)
What must happen to chromosomes during cell divison?
They must be accurately copied and passed on.
What is cell division?
The process of replicating cells to make new ones.
What are the two types of cell divison?
Mitosis and meiosis.
Describe the process of mitosis.
How long does mitosis take?
At its fastest, one hour.
What is mitosis used for?
- Growth/repair of tissues (replacement)
- In asexual reproduction
- Cloning
What cell cannot duplicate?
Nerve cells cannot perform mitosis, and therefore can never repair. Once damaged, they cannot be fixed.
Describe the process of meiosis.
What is meiosis used for?
Creating Gametes
What is crossing-over?
When homologous chromosome pairs exchange DNA to create genetic variation.
How many cell divisions take place in mitosis?
One
How many cell divisions take place in meiosis?
Two
How many daughter cells are created in mitosis?
Two
How many daughter cells are created in meiosis?
Four
What is an allele?
A different version of the same gene.
What does homozygous mean?
When both alleles are the same (eg BB or bb)
What does heterozygous mean?
When both alleles are different (eg Bb)
What is the genotype?
Which alleles you have (eg BB, Bb or bb)
What is the phenotype?
The outward expression of the alleles you have / your appearance. (eg blue eyes)
What is a dominant allele?
You only need one allele present for the characteristic to be expressed in the phenotype.
What is a recessive allele?
You need two copies of the same allele for the characteristic to be expressed in the phenotype.
What is a codominant allele?
When two alleles of the same gene are both expressed in the phenotype.
What does diploid mean?
The full number of chromosomes are in the cell (46 in humans) and there are two of each pair of chromosomes.
What does haploid mean?
Half the number of chromosomes (gametes only) and there is only one of each pair of chromosomes.
