Subtopic (b) Inheritance

SQA questions

Inheritance WYSK• Certain characteristics are determined by g_______

i_________ received from both p_______ e.g. fur c______ , blood g______, stem l_______ and shape of l______ or seeds

• Each inherited characteristic can appear in a number of forms called p__________.

• Phenotype is the a__________ of an individual• An organism which is t________ b________ e.g. TT

or gg produces only o___ type of gamete e.g. _ or _• The F1 offspring of a true breeding cross have

u_______ phenotype – all the same

eneticnformation arentsolour roup ength

eaves

henotypesppearance

rue reeding ne T g

niform

• A d_________ gene or phenotype always shows• A r__________ gene or phenotype can be hiddenA m__________ cross is between two true breeding

parents which have d_______ phenotypes of the s_______ characteristic E.g. Black (BB) x brown (bb)

• The symbol for parental generation is __• The symbol for first offspring is __• The symbol for second offspring is __The expected ratio in F2 is _____ ( ¾ : ¼ )Expected ratios don’t always happen because

f____________ is a r_________ process

ominantecessiveonohybrid

ifferentame

PF1

F23 : 1

ertilisation random

• A parent contributes o___of the two forms of a gene to their o________

• A g________ is a sex cell which carries o___ of the two forms of a gene

• Gametes contain a s________ set of chromosomes• Body cells contain a d________ set of chromosomes

– t___ matching sets• The r_________ in the number of chromosomes

occurs at g_______ formation• At fertilisation chromosome numbers d________

when the m_____ nucleus and the female n_______ fuse together

neffspring

amete ne

ingleouble

eductionamete

oubleale ucleus

wo

• A g____ is part of a chromosome. T___ forms of a gene control each inherited characteristic

• The genotype is all the g______ an organism contains. Its genetic m____ - up.

A______ is the name given to the two forms of a gene

• The __ and ___ chromosomes determine sex• ___ is male and ___ is female• The male gamete (s______) may contain an __ or a

__ chromosome• The female gamete (e___) always contains an ___

chromosome

ene wo

enesake

llele

X YXY XX

perm XY

gg X

Llama and camel successfully interbreed to produce baby

Scientists believe he will be infertile

XYXX

XY XX

G

tongue rolling sex blood groups ear lobes

Presence of operation scars

G

√ gametes

√

√ doubled

G

horns

F1

G

gold body black body

black body

bb BB

Bb

bbBB or Bb

G

4 : 1

84 black body : 21 gold body

Divide by 21: 84÷ 21 21 ÷ 21

= 4 : 1

G

√

discontinuous

gametes

G

taster non taster

√

G

Use the letters T for tasting and t for non tasting to show the forms of gene present in the sex cells of Rab and Audrey

t t

G

gametes

√

X YX X

Down’s syndrome

G

X X X Y

female male

F1

G

genotype

gamete

variation

G

Two/double Two/double

Two/double

one/single one/single

gametes

fertilisation

G

X XXY

XY XX

female female

G

discontinuous

Arranged in distinct / clear cut groups

C

195 yellow seeds + 65 purple seeds = 260 seeds

% yellow : 195÷ 260 = 0.75 X 100 = 75%

75%

alleles

radiation

C

GG

Gg

5418

¼ of 72 = 18 black

¾ of 72 = 54 grey

C

Fertilisation is a random process

alleles

C

TT tt

Tt

3 1

C

4 1

Fertilisation is a random process

C

alleles

bb Bb

Fertilisation is a random process

C

bb

Same coat colour

discontinuous

C

all

nonesome

RR rr

Rr Rr

1RR : 2Rr : 1rr

C

496

Fertilisation is a random process

Rrrr

ratio is 3 red : 1 white

1488 ÷ 3 = 496 white

C

alleles

Can be arranged into distinct (clear cut) groups

C