Key concepts - Hereditary & Reproduction

Question 1

The role of genes and chromosomes in heredity

Answer 1

Chromosome has DNA, DNA has genes.
Genes are a segment of a DNA molecule that codes for a particular trait.
Genes code for proteins which are the building blocks of the body and heredity.

Question 2

Advantages of asexual reproduction

Answer 2

Do not need to seek out a mate

No specialized mating behaviours

No specialized anatomy

Nothing left to chance – heredity is direct & invariable.

Question 3

Disadvantages of asexual reproductions

Answer 3

Invariable offspring means that if the environment changes, individuals may no longer be suited to survive.

Question 4

Advantages of sexual reproduction

Answer 4

Offspring are not genetically identical to parents or to each other

Variability in offspring means that if the environment changes, some of the offspring are better adapted and survive.

Question 5

Disadvantages of sexual reproduction

Answer 5

Need to have specialized organs, mating calls or brightly coloured, etc…

Sex is biologically “costly” – attracting a mate can also attract predators (and your too busy head butting or dancing so you get eaten)

Requires two members of the species to interact

Question 6

Number of chromosomes

Answer 6

46 chromosomes (23 pairs)

Question 7

Evolution of chromosomes

Answer 7

Tightly bound bodies of DNA
One chromosome in each pair is from your parents

Question 8

Types of asexual reproduction

Answer 8

Budding: producing offspring by outgrowths of their body
Fragmentation: when a piece breaks off and becomes independent

Question 9

Structure of chromosomes and chromatids

Question 10

Number of chromosomes in a diploid cell

Answer 10

contain the normal number (46 (23 pairs))

Question 11

Number of chromosomes in a haploid cell

Answer 11

Half the normal number

Question 12

(Mitosis) 0. Interphase

Answer 12

During interphase genetic material in the form of thread-like chromatin is duplicated (replication)
This results in the pairs of sister chromatids.

Question 13

(Mitosis) 1. Prophase

Answer 13

During prophase the chromatin (chromosomes) shorten and thicken and are visible under a microscope
Centrioles (in animal cells) separate and move to opposite ends of the cell
Nuclear membrane starts to dissolve

Question 14

(Mitosis) 2. Metaphase

Answer 14

Spindle fibers move and align chromosomes (each composed of sister chromatids) in the centre (equator) of the cell

Question 15

(Mitosis) 3. Anaphase

Answer 15

Sister chromatids divide (now called chromosomes)
Sister chromatids split at the centromere and move to opposite poles of the cell
If mitosis proceeds correctly, the same number of chromosomes will be found at each pole of the cell

Question 16

(Mitosis) 4. Telophase

Answer 16

Chromosomes reach opposite poles of the cell and begin to disappear (go back to being chromatin)
Spindle fibers disappear
Nuclear membrane re-forms
Two identical daughter cells are now present

Question 17

(Mitosis) 4b. Cytokinesis

Answer 17

The cell divides its cytoplasm and organelles into two new daughter cells
In many cells (protists, fungi & animal cells) a furrow develops
In plant cells, a cell plate appears on the equator. This becomes the cell wall

Question 18

Process of cloning animals

Answer 18

The process involved substituting the desired nucleus in place of the original nucleus

Question 19

Genes

Answer 19

codes for a trait: hair colour

Question 20

Alleles

Answer 20

variation that you possess: brown, black, red, blond hair

Question 21

Phenotype

Answer 21

represents the outward appearance of the individual according to their genotype

Question 22

Genotype

Answer 22

genetic makeup of the individual: which genes they possess.

Question 23

Dominance

Answer 23

will always show up if in the genotype

Question 24

Recessiveness

Answer 24

will only show up if there’s no dominant gene

Question 25

Meiosis

Answer 25

The process by which these alleles are separated into the gametes. Sexual reproduction depends on meiosis It is a process involving two stages in which the resulting daughter cells have half the number of chromosomes (haploid) as the parent cell Results in the formation of haploid sex cells (eggs & sperm)

Question 26

Law of segregation

Answer 26

Each parent passes one, and only one, allele to their offspring. Since a pair of chromosomes carries two alleles, only one chromosome can be passed along.

Question 27

Random Assortment

Answer 27

The number of possible combinations of chromosomes depends on the chromosome pairs, for diploid (2n) organisms the number of possible combinations is 2n