bio chap 13 inhertiance

Question 1

what is inheritance

Answer 1

transmission of traits from one generation to another

Question 2

what is monohybrid inhertitance?

Answer 2

inheritance of one distinct physical characteristic controlled by a particular gene

Question 3

what are the 6 things to include in punnet squares

Answer 3

legend

parental phenotype and genotype

gametes

punnet square

f2 genotupe

phenotypic ratio

Question 4

what is a chromosome

Answer 4

tightly coiled dna molecule
carries many genes along its length
position of each gene in chromosome is called a gene locus

Question 5

what is a gene

Answer 5

sequence of dna nucleotides that controls the formation of a single polypeptide

a unit of inheritance

codes for the production of a protein that controls a particular characteristic in an organism

Question 6

what is an allele

Answer 6

different forms of the same genes
occupy the same relative position in a particular pair of homologous chromosomes

Question 7

what are homologous chromosomes

Answer 7

2 chromosomes in a pair which have the same size, shape and sequence of genes

one inherited from mother and one from father

same sequence of genes that may have same or different alleles

Question 8

what is a phenotype

Answer 8

expressed trait or an outward appearance or visible characteristics of an organism

external - such as height, eye colour
internal - human blood groups/ resistance to certain diseases

Question 9

what is a genotype

Answer 9

genetic make up of an organism, combination of alleles for a particular gene

dominant: an allele that is almost always expressed even if only one copy is present TT/Tt

recessive: a gene that is phenotypically manifest in the homozygous state
masked in the heterozygote by the presence of a dominant allele -> tt

Question 10

what is homozygous

Answer 10

2 of the same alleles at a given locus on homologous chromosomes -> TT/tt

Question 11

what is heterozygous

Answer 11

2 different alleles at a given locus on a pair of homologous chromosomes -> Tt

Question 12

will the offspring have an equal chance of being male or female

Answer 12

Yes

Question 13

what is the number of chromosomes in body cells and gametes of males

Answer 13

body cells -> 44 non sex chromosomes + X + Y

gametes -> 22 non sex chromosomes + X OR + Y

Question 14

what is the number of chromosomes in body cells and gametes of females

Answer 14

body cells -> 44 non sex chromosomes + X + X

gametes -> 22 non sex chromosomes + X

Question 15

what is variation

Answer 15

differences in traits between individuals of the same species

Question 16

what is discontinuous variation

Answer 16

controlled by 1 or few genes
- clearly defined differences with few or no intermediate forms between traits
- the traits are easily distinguishable and are not affected by environmental conditions

Question 17

how to differentiate continuous and discontinuous variation

Answer 17

phenotypes
- c: range of phenotypes
- d: few clear cut phenotypes

controlled by
- c: many genes
- d: one or a few genes

shows additive effect
- c: yes
- d: no

affected by environmental conditions
- c: yes
- d: no

Question 18

what is mutation

Answer 18

change in the sequence of a gene or in chromosome number

can be inherited -> passed down through gametes from parents to offspring

Question 19

what is gene mutation

Answer 19

occurs randomly and spontaneously when a cell divides and produces variation within individuals

Question 20

what is albinism

Answer 20

recessive gene mutation
individuals who are homozygous for the albinism allele are albinos

characterised by the absence of pigments in the skin hair and eyes
-> reddish-white skin and white hair

iris does not contain any pigment and may appear red because of the colour of blood vessels in it

albinos are very sensitive to sunlight and their skin can get sunburnt easily

Question 21

what is sickle cell anaemia

Answer 21

results in change in structure of gene
change in the sequence of bases or nucleotides in the dna

sickle cell rbc
- encodes haemoglobin S protein in rbc
> HbS almost same as normal haemoglobin A
-> change in 3d shape of haemoglobin molecule -» HbS molecules clump tgt to be sickle shaped

phenotype
people who have homozygous recessive have abnormal haemoglobin in their RBC
when o2 conc in blood decreases RBC becomes sickle shaped

Question 22

what is chromosome mutation

Answer 22

change in the number of chromosomes in an organism

Question 23

what is down syndrome

Answer 23

have one extra chromosome -> 47 in body cells
normally zygotes w an extra chromosome would fail to develop
- exception: zygote w an extra copy of chromosome 21

Question 24

what are the possibilities that chromosome 21 has an extra chromosomes

Answer 24

the older the mother -> the higher the chance that copies of chromosome 21 will not separate during gamete formations

possible for mutation to occur in sperm that carry an extra chromosome 21

Question 25

what are mutagens

Answer 25

rate of spontaneous mutation is usually very low rate of mutation greatly increases with presence of certain agents i external environment -> mutanic agents: mutagens ionising radiation that are mutagenic includes - uv light - alpha, beta, gamma radiations some chemics are mutagenic if present in certain concs - formaldehyde and tar found in cig moke - lysergic acjd diethylamide ( LSD )drug

Question 26

explain mutation and selection

Answer 26

some mutations will disrupt normal functions of a cell which is harmful or lethal to an organism some mutations are beneficial - allow an individual to avoid predators with better chromosomes leave more offspring than individuls without beneficial mutation frequency of mutant allele will increase in population of organism organisms w new traits may ariss after many years, gvg rise to new species nature selects those organisms w more favourable traits to survive and reproduce evolution and present day forms of life is believed to have occured through mutation and natural selection