chapter 5: genetics Flashcards
Human chromosomes consist of
- 22 pair autosomes
- 1 pair of sex chromosomes (X chromosome and Y chromosome)
What is mitosis
is a cell division process that forms 2 identical daughter cells, each having the same number of chromosomes and genetic content as parent cell
- mitosis takes place in somatic cells of human and animal bodies / meristematic tissue such as the tip of the roots and the shoot of the plant
What is meiosis
a process where the cell divides into 4 distinct cells, each containing half the number of chromosomes in the parent cell.
- takes place in the reproductive organ to produce gametes for sexual reproduction
- takes place in male’s testes and female’s ovary
- in plant, in anther and ovary
Process of mitosis
1) prophase
- chromosomes shorten and thicken and become visible
- each chromosome consists of 2 chromatids bound to the centromere
2) metaphase
- chromosomes are arranged in equatorial
- spindle fibres are fully formed
3) anaphase
- the centromere divides into 2
4) telophase
- chromatids reach the opposite poles
- nuclear membrane and nucleolus are formed again
Process of meiosis
1) Prophase I
- chromosome shorten and thicken, and become visible
2) Metaphase I
3) Anaphase I
4) Telophase I
5) Prophase II
6) Metaphase II
7) Anaphase II
8) Telophase II
Similarities between mitosis and meiosis
1) DNA replication
2) cell divisiond
Differences between mitosis and meiosis
Mitosis
1) takes place in somatic cell
2) produce 2 daughter cells
3) NO crossing over
4) daughter cell identical to their parent cells
5) NO variation
6) number of chromosomes of daughter cells is same with parents cell
Meiosis
1) take place in reproductive cell
2) produce 4 daughter cells
3) crossing over occurs
4) daughter cells not identical to their parent cells
5) has variation
6) the number of chromosomes of the daughter cell is half the parent cell
Importance of mitosis and meiosis
mitosis: growth of organisms / replace damaged or dead cells when we injured / asexual reproduction of organisms such as amoeba sp
meiosis: production of gametes
list out dominant trait
1) can roll tongue
2) free earlobe
3) have dimples
4) black hair
list out recessive trait
1) cant roll tongue
2) attached earlobe
3) doesnt have dimples
4) blonde hair
Type of mutations and list out
1) CHROMOSOME MUTATION
- down syndrome
- turner syndrome
- klinefelter syndrome
2) GENE MUTATION
- colour blindness
- sickle cell anaemia
- thalassemia
- haemophilia
- albinism
What is down syndrome
- has an extra chromosome in chromosome number 21
- total number chromosomes is 47
- characteristics: mental and physical disabilities, round and flat face, short neck
What is turner syndrome
- has less number of sex chromosomes
- total number of chromosomes is 45 chromosomes ( 44+XO)
- a person wtih turner syndrome is a female who has a missing X chromosome
- characteristics: undeveloped secondary sexual characteristics of a female
What is klinefelter syndrome
- has more number of sex chromosomes
- total number of chromosomes is 47 chromosomes (44 + XXY)
- is a male with an extra chromosome X
- chracteristics: has female characteristics like breasts, small testicles, low sperm count
what is colour blindness
- unable to differentiate between red and green
- controlled by recessive genes on chromosome X
- usually occurs in males
What is sickle-cell anaemia
- cause by recessive genes on the autosome
- has an abnormal red blood cell shape that is sickle-shaped that affects the transport of oxygen
What is thalassemia
- the person has small, pale, red blood cells that easily burst and have short life span
- cause severe blood loss
What is haemophilia
- difficulty in the clotting of the blood
- faces risk of continuous blood loss if wounded or injured
Application of genetic research to improve quality of life
1) gene therapy
- repair mutant genes (abnormal) that cause disorder such as haemophilia, sickle-cell anaemia
2) forensic science
- obtain scientific evidence in criminal investigation
3) genetic genealogy
- use DNA test to determine genealogy heredity and family history
What is recombinant DNA technology
- combines the DNA of 2 different species to produce a new genetic characteristic
- the production of human insulin by bacteria to help patients with diabetes
the effects of genetic engineering technology in life
Advantages
1) can detect genetic failure/ familial disease and treat it
2) produce high quality yield and livestock
3) produce yield with faster growth rate and shorter harvesting period
4) increase yield and livestock
Disadvantages
1) can cause side effects or allergies to consumers
2) production of new species may cause the native species to become extinct
What is continuous variation and discontinuous variation
CONTINUOUS VARIATION
shows the differences that are not distinct or not clear between individual in the same population
- determined by genetic factors but can also be affected by environmental factor
- example: height, body mass, length of fingers
DISCONTINUOUS VARIATION
- shows distinct differences between individuals of the same population
- determined by genetic factors
- example: shape of earlobes, the ability to roll tongue
Factors that cause variation
GENETIC FACTOR
1) crossing over during prophasi I stage of meiosis
2) independent arrangement of chromosomes
3) random fertilisation between male and female gametes produces zygotes with different combination of geotypes
4) chromosome and gene mutation
ENVIRONMENTAL FACTORS
1) nutition
2) PH
3) temperature
4) climate
5) sunlight
6) water
example: overeating will make a person fat/ skin colour will be darker if often exposed to sunlight
what is the importance of variation
- enables us to easily differentiate and recognise each individual
- anables the organisms to adapt themselves to their environment
