Patterns Of Inheritance-6.2

Question 1

What is genotype?

Answer 1

-the genetic constitution of an organism(the alleles it has for a gene)

Question 2

What is phenotype?

Answer 2

-the visible characteristics of an organism
-due to interactions of the genotype and the environment

Question 3

What contributes to phenotypic variation?

Answer 3

-both environmental and genetic factors

Question 4

What are gene mutations ?

Answer 4

-a genetic factor for phenotypic variation
-mutations can be harmful,advantageous or neutral

Question 5

What are two things that mutations that occur during gamete formation are?

Answer 5

-persistent-they can be transmitted through many generations without change
-random-they are not directed by a need on the part of the organism which they occur

Question 6

What are chromosome mutations?

Answer 6

-a genetic factor for phenotypic variation
-chromosome mutations may occur during meiosis

Question 7

What are mutagens?

Answer 7

-certain physical and chemical agents that can increase the rate of mutation
-e.g.
physical agents- X-ray, UV light
Chemical agents-mustard gas, nitrous acid
Biological agents -some viruses, food contaminants such as mycotoxins from fungi

Question 8

What is deletion in relation to chromosome mutations?

Answer 8

-part of the chromosome, containing genes and regulatory sequences is lost

Question 9

What is inversion in relation to chromosome mutations?

Answer 9

-a section of the chromosome may break off, turn through 180 degrees and then join again
-although the genes are all still present some may now be too far away from their regulatory nucleotide sequences to be properly expressed

Question 10

What is translocation in relation to chromosome mutations ?

Answer 10

-a piece of chromosome breaks off and then becomes attached to another chromosome
-this may also interfere with the regulation of the genes on the translocated chromosome

Question 11

What is duplication in relation to chromosome mutations ?

Answer 11

-a piece of a chromosome may be duplicated
-over expression of genes can be harmful ,because too many of certain proteins or gene-regulating nucleic acids may disrupt metabolism

Question 12

What is non-disjunction in relation to chromosome mutations ?

Answer 12

-one pair of chromosomes or chromatids fails to separate, leaving one gamete with an extra chromosome
-when fertilised by a normal haploid gamete ,the resulting zygote has one extra chromosme
-down syndrome or trisomy 21 is caused by non-disjunction

Question 13

What is aneuploidy in relation to chromosome mutations ?

Answer 13

-the chromosomes number is not an exact multiple of the haploid number for that organism
-sometimes chromosomes fail to separate during meiosis e.g trisomy

Question 14

What is polyploidy in relation to chromosome mutations?

Answer 14

-if a diploid gamete is fertilised by a haploid gamete
-the resulting zygote will be triploid (it has three sets of chromosomes )
-the fusion of 2 diploid gametes can make a tetraploid zygote
-many cultivated plants are polyploid- they have more than 2 sets of chromosomes

Question 15

Genetic variation resulting from sexual reproduction has contributed to …

Answer 15

-evolution

Question 16

What may lead to genetic variation during meiosis ?

Answer 16

-allele shuffling (swapping of alleles between non-sister chromatids ) during crossing over in prophase 1
-independent assortment of chromosomes during metaphase/anaphase 1
-independent assortment of chromatids during metaphase/anaphase 2

Question 17

What does random fusion of gametes at fertilisation lead to?

Answer 17

-creates more genetic diversity
-any male gamete can potentially combine with any female gamete from an organism of the same species
-the random fertilisation of gametes that are already genetically unique produces extensive genetic diversity among the resulting offspring

Question 18

What are 2 characteristics of gametes produced by meiosis?

Answer 18

-individual and genetically dissimilar
-haploid -containing only one of each pair of homologous chromosomes and one allele for every gene

Question 19

What are some examples of environmental factors that causes variation?

Answer 19

-having a scar following an injury
-diet of an animal influencing weight
-etiolation-a condition in plants characterised by weak stems and small pale leaves due to insufficient exposure to light

Question 20

What is an allele?

Answer 20

-a version of a gene

Question 21

What does heterozygous mean?

Answer 21

-a pair of homologous chromosomes carrying two different alleles for a single gene
-not true-breeding/non pure breeding

Question 22

What does homozygous mean?

Answer 22

-a pair of homologous chromosomes carrying the same alleles for a single gene
-true-breeding/pure breeding

Question 23

What does monogenic mean?

Answer 23

-determined by a single gene
-can be visualised using a punnett square

Question 24

What is a monohybrid cross?

Answer 24

-genetic inheritance cross of a characteristic determined by one gene
E.g. punnett square

Question 25

What must you show in a genetic cross?

Answer 25

1-parental phenotype
2-parental genotype
3-possible gametes
4-offspring genotype
5-offspring phenotype
6-proportion of each phenotype (phenotypic ratio)

Question 26

What does F1 generation stand for?

Answer 26

-first filial generation

Question 27

What do you always circle when doing genetic crosses?

Answer 27

-gametes

Question 28

What is F2 generation?

Answer 28

-second generation

Question 29

What is the test cross?

Answer 29

-a method used to work out the unknown genotypes of individual organisms that is expressing a dominant phenotype

Question 30

How is a test cross done?

Answer 30

The individual in question is crossed with an individual that is expressing the recessive phenotype
The resulting phenotypes of the offspring provide sufficient information to suggest the genotype of the unknown individual
If there are any offspring expressing the recessive phenotype then the unknown individual must have a heterozygous genotype

Question 31

What is dihyrid?

Answer 31

-genetic inheritance cross for a characteristic determined by 2 genes
-it involves 2 gene loci