Inheritance

Question 1

What are chromosomes?

Answer 1

• thread-like structure of DNA which carries genetic info of cell
• found in nucleus of animal cells

Question 2

What is DNA and its structure?

Answer 2

• molecule that contains the genetic instructions for development + function of organism
• double helix structure (sugar phosphate backbone with base pairs AT, GC linked by hydrogen bonds)

Question 3

What is a gene?

Answer 3

A section of DNA (group of base pairs) that codes for formation of a protein controlling specific characteristic of an organism

Question 4

What is an allele?

Answer 4

different versions of the same gene

Question 5

How is sex inherited/determined by genes?

Answer 5

• 1 pair of chromosomes (sex ones) determines sex

- The pair can either be XX for female and XY for male

Question 6

What is the difference between haploid and diploid?

Answer 6

• haploid cells contain one set of unpaired chromosomes

- diploid cells contain 2 sets of chromosomes with each type having a pair

Question 7

How many chromosomes do somatic body cells and sex cells have?

Answer 7

• BODY CELLS = 46 chromosomes, 23 pairs
  (22 pairs autosomal chromosomes, 1 pair sex chromosome XX, XY)
• sex cells = 23 chromosomes
  (22 autosomal chromosome, 1 sex chromosome X or Y_

Question 8

What is mitosis?

Answer 8

cell division that produces 2 genetically identical daughter cells (each 2n)
- used for growth, reproduction of cell

Question 9

What is meiosis?

Answer 9

cell division producing 4 daughter cells (each n)

- PRODUCES SEX CELLS (gametes)

Question 10

What are the names of the bases and their pairings?

Answer 10

Adenine - Thymine

Guanine - Cytosine

Question 11

What are dominant and recessive alleles?

Answer 11

• Dominant gene always shown in phenotype
• recessive is still existent but masked by dominant
  (only shown in recessive homozyg. tt)

Question 12

what is the genotype and phenotype?

Answer 12

Genotype = genetic makeup of organism (ie. TT, Tt, tt)

Phenotype = visible characteristics of organism

Question 13

What do family pedigrees show?

Answer 13

the inheritance of an allele over generations

Question 14

What is co-dominance?

Answer 14

• when 2 heterozygous alleles are expressed (ie. blood type A + blood type B = blood type AB)

Question 15

What is incomplete dominance?

Answer 15

• blending of parent alleles that results in a third phenotype that doesn’t look like either of parents

Question 16

What is a sex-linked characteristic?

Answer 16

• A characteristic where the gene responsible is located on a sex chromosome
• THEREFORE it is more common in one sex than another (ie. female carriers of colour blindness)

Question 17

What is a mutation?

Answer 17

• changes to the DNA sequence or chromosome number

- new phenotypes can ONLY appear in a population after a mutation event

Question 18

What is a mutation?

HOW DOES IT OCCUR AND WORK?!

Answer 18

• changes to the DNA sequence or chromosome number

- new phenotypes can ONLY appear in a population after a mutation event

Question 19

What are the types of mutation?

Answer 19

1. point mutation
2. frame shift
3. parts or whole chromosome involved

Question 20

What can cause mutation in genes and chromosomes?

Answer 20

1. errors in DNA replication
2. errors in cell division
3. damage by physical or chemical factors

Question 21

What are the 3 modes of inheritance?

Answer 21

1. Autosomal dominant/recessive
2. Sex linked (X linked) dominant recessive
3. Incomplete dominane

Question 22

Why does sex linked inheritance occur?

Answer 22

traits are more common to one gender as the missing arm on Y chromosome means for some trait, only one allele (X) is present and can contribute to phenotype

Question 23

why can only females be carriers and only men be affected & possess the trait?

Answer 23

• men do not have another allele to dominate over defective allele
• female has another allele inherited from other parent (normal + dom.) but can carry the trait as it is recessive and still existent but masked

Question 24

what is fertilisation?

Answer 24

union of female and male gametes (sperm + egg) to produce a zygote

Question 25

What are the processes involved in the formation of a new individual?

Answer 25

1. Meiosis
2. fertilisation
3. mitosis

Question 26

why do sex cells have half the no. of chromosomes of (somatic) body cells

Answer 26

to maintain the fixed no. of chromosomes in a species, gametes need to have half the no. of chromosomes of a somatic cell

(restored in fertilisation when the gametes fuse to produce zygote)

Question 27

factors that increase rate of mutations?

Answer 27

• high energy radiation (UV, x-rays, gamma rays)
• carcinogenic chemicals
• extreme heat

Question 28

causes of mutation

Answer 28

• errors in DNA replication
• errors in cell division
• damage by physical/chemical factors

Question 29

how mutation can occur

Answer 29

1. point mutation
2. frame shift
3. parts or whole chromosome involved

Question 30

What is mutation

Answer 30

changes to the DNA sequence or chromosome no.

- new phenotypes can only appear in population after mutation event

Question 31

what are the 2 types of mutation

Answer 31

1. gene mutation: change in the DNA sequence of gene (eg. sickle cell anaemia)
2. chromosomal mutation: change in the no. of chromosomes (eg. Down’s syndrome)

Question 32

what are the genotypes of symbols X^H, X^h, Y

Answer 32

X^HY, X^hY, X^HX^H, X^HX^h, X^hX^h