The Genome, Chromosomes, DNA And Genetics Flashcards
(52 cards)
1
Q
what is a chromosome?
A
A long strand of DNA located in the nucleus
2
Q
What is a gene? (2)
A
- A short strand of DNA (part of a chromosome)
- that codes for a particular characteristic
3
Q
What is an allele?
A
- An alternative form of gene
- for a particular characteristic
4
Q
Define Gene Locus
A
The position of a gene on a chromosome
5
Q
What is independent assortment? (3)
A
- A process that takes place during meiosis
- in which chromosomes are reassorted
- in the formation of gametes
6
Q
What is meiosis? (3)
A
- A type of cell division
- that produces cells (gametes)
- that have half the normal chromosome number (haploid cells)
7
Q
What is mitosis? (3)
A
- A type of cell division
- that produces cells genetically identical
- to the parent cell and each other
8
Q
What is the genotype of an allele?
A
- The genetic arrangement of alleles (genetic make up)
- for 1 or more traits
9
Q
What is meant by phenotype? (2)
A
- The actual appearance of alleles (genetic make up)
- for 1 or more traits
10
Q
What is meant by the term homozygous?
A
if the individual has two identical alleles for a characteristic
e.g. AA or aa
11
Q
What is meant by the term heterozygous?
A
If the individual has two different alleles for a characteristic
E.g. Aa
12
Q
What is meant by the term recessive?
A
The allele that is only expressed in the homozygous form
E.g. aa
13
Q
What is meant by the term dominant?
A
The allele that is expressed in both the homozygous and heterozygous forms
E.g. AA or Aa
14
Q
What is heredity? (2)
A
- The transfer of genetic information (alleles)
- from one generation to the next
15
Q
What are homologous chromosomes? (3)
A
- A pair of chromosomes
- that are the same length
- and have genes for the same characteristics
(The alleles present may be different)
16
Q
What is monohybrid inheritance?
A
When only one trait (gene) is considered in a genetics cross
17
Q
What is a back/test cross? (2)
A
- a test carried out to confirm the genotype of an individual
- with a pure bred homozygous recessive
(I.e. to determine if the individual is heterozygous or homozygous dominant)
18
Q
What are the stages of meiosis? (2)
A
- where one cell divides into two
- the two cells divide to form a total of four cells
19
Q
What is a genetic disorder? (2)
A
- A disease caused by errors in a DNA sequence,
- disorders are heritable so can potentially be passed on to offspring
20
Q
What is Cystic Fibrosis? (2)
A
- A genetic disorder of the cell membranes that leads to excess mucus that damages organ systems,
- caused by a recessive allele
21
Q
How is cystic fibrosis inherited?
A
only if two recessive alleles are present
22
Q
What is a carrier? (2)
A
- An individual who carries a recessive allele for a disorder
- but does not express the disorder’s phenotype
23
Q
What is haemophilia? (2)
A
- An inherited condition characterised by an inability to clot blood
- haemophilia is a sex-linked condition
24
Q
How is haemophilia inherited? (2)
A
- it is a sex-linked disorder, meaning it is found on the X-chromosome
- It takes two of the allele for a woman to get the disorder, but only one is required for a male
25
What are **sex-linked disorders**? (**2**)
- A **genetic condition** caused by **genes** on the **23rd chromosomes** or the **X or Y chromosome**
- they only require **one** copy of an **allele** for **male inheritance**, but **two for females**
26
What is **Huntington’s disease**? (**2**)
- A **genetic disorder** that causes **progressive deterioration of brain cells**,
- **does not appear until older age**
27
How is **Huntington’s disease inherited**? (**2**)
It is expressed by a **dominant allele**, it will always be expressed unless an individual is **homozygous recessive**
- you **cannot be a carrier** for **dominant disorders**
28
What is **Down syndrome**?
A condition of **intellectual disability** and associated **physical disorders**
29
How is **Down syndrome inherited**? (**2**)
- Caused by a genetic trait known as **trisomy**, where an **additional copy of the 21st chromosome** is present,
- it results from an **extra chromosome** to make a total of **47 rather than 46**
30
What are the **X and Y** chromosomes?
- the **23rd pair of chromosomes** in a human,
- the combination of these determines the sex of an offspring
31
What **gender** is given by **XX**
What is the **probability** of them **having a XX child**?
- female
- 50%
32
What **gender** is given by **XY**
What is the **probability** of them **having a XY child**?
- male
- 50%
33
How many **chromosomes** are **in human cells**? How are they **arranged**?
46 —> in 23 pairs
34
How many **chromosomes** are **in human gametes**?
23
(*Half the normal number*)
35
How is **insulin produced**? (**8**)
- use **restriction enzyme** to remove **human insulin gene**
- remove **plasmid** from bacterium
- **cut plasmid open** using **restriction enzyme**
- implant **insulin gene into plasmid**
- put **plasmid into bacterium**
- place **bacteria in fermenter** with optimum pH, temp, nutrients etc.
- bacteria **reproduce**
- **downstreaming**: extract, purify and pack insulin
36
Describe how the **insulin gene** can be incorporated **into** the **plasmid** (**3**)
- **restriction enzyme** *cuts* **insulin gene** from human DNA
- **same restriction enzyme** *cuts plasmid* **open**
- insulin gene joins plasmid due to **complementary sticky ends**
37
What is the **structure of DNA**?
Double Helix
38
What is meant by the **genome** of an organism?
**All** the **DNA** *in an organism*
39
what are the **three components of DNA** - what are they represented with in diagrams?
- phosphates - circles
- sugars - pentagons
- bases - blocks with names
40
What are the **4 bases**? Which **link** together?
- adenine
- thymine
- cytosine
- guanine
**AT
CG**
41
What **connects bases** in DNA?
Hydrogen bonds
42
What **term** describes a **phosphate, sugar and base**
A nucleotide
43
What is a **base triplet**? (**2**)
- The **sequence of three bases** on a **single strand** of DNA
- that **codes** for an **amino acid**
44
What are the **three uses** of **Mitosis**?
- growth
- repair of damaged tissue
- replacing worn out cells
45
What is **genetic engineering**? (**2**)
- A process that **modifies the genome** of an organism
- to **introduce desirable characteristics**
46
Where are **restriction enzymes** used? **How** do they **cut**? (**2**)
- In **extraction** of the **human insulin gene** and **cutting open** a bacterial **plasmid**
- they leave **sticky ends** for the **other gene to bond**
47
What is **Amniocentesis**? (**2**)
- The **extraction of foetal cells** from amniotic fluid (by a needle) for examination,
- to **test for genetic abnormalities**
48
name **two sex-linked disorders**
- colour blindness
- haemophilia
49
What is the **name** of *cells* with **half the number of chromosomes**?
Haploid cells
50
What is the **name** of *cells* with a **normal number of chromosomes**?
Diploid cells
51
**How** does the **DNA** of *individuals **differ***?
Each person has **different base sequences**
52
What are **karyotypes**?
An individual’s **complete set of chromosomes**
