a2 genetics unit f215 genetics
Post on 04-Feb-2018
236 Views
Preview:
TRANSCRIPT
-
7/21/2019 A2 Genetics Unit F215 Genetics
1/21
A2 Unit F215: Module 1
Control, genomes and environment
Module 1 Cellular control
Genetics
Gregor Mendel the Austrian monk who irst investigated genetics o !lant "reeding#
-
7/21/2019 A2 Genetics Unit F215 Genetics
2/21
A2 Unit F215: Module 1Control, genomes and environment
Module 1 Genetics
$o!ic Tick when
done
%a& '(!lain the termsgenot)!e, !henot)!e, dominant, recessive,
codominance and linkage#
%"& Use genetic diagrams to solve !ro"lems involving se(*linkage#
%c& Use genetic diagrams to solve !ro"lems involving codominance
%d& +escri"e the interactions "etween loci %e!istasis&
%e& redict !henot)!ic ratios in !ro"lems involving e!istasis#
%& Use !redicted !henot)!ic ratios to solve !ro"lems involving e!istasis#
%g& Use the chi*s-uared test to test the signiicance o the dierence
"etween o"served and e(!ected results#
%h& +escri"e the dierences "etween discontinuous and continuous
variation#
%i& '(!lain the "asis o continuous and discontinuous variation with
reerence to the num"er o genes that inluence the variation#
%.& '(!lain that "oth genot)!e and environment contri"ute to
!henot)!ic variation and wh) variation is essential in selection#
-
7/21/2019 A2 Genetics Unit F215 Genetics
3/21
G'/'$0C $'M0/3G4
GENE a length o 6666 that codes or the !roduction o a
66666666666 molecule#
GENETIC CODE
ALLELES dierent formso one gene, e#g777777
LOCUS the positiono a gene on a 666666666666666 and on its
homologous !artner#
GENOTYPE the 2 alleles which an organism !ossesses or a !articulargene, e#g# GG, Gg or gg# %From whom did the organism inherit each one8&
PENOTYPE the e!pressiono the "enot#pee#g# a !erson either has
c)stic i"rosis or not#
DO$INANT onl) oneo this allele needs to "e !resent or the allele
to "e 66666666666666 in the !666666666#
%ECESSI&E twoo these alleles need to "e !resent or7777##
CODO$INANCE 'oth ())e)es (re e*+())# e!pressed in the
,,,,,,,,,, of ( hetero-#"ote.
So 'oth C % /red pi"ment0 (nd
C1
/white pi"ment0 (re e!pressed if to"ether in( "enot#pe. The phenot#pe wi)) therefore 'e222..
LIN3AGE 4 5 or more "enes (re )oc(ted /)inked0 on the s(me
chromosome.
A 6
-
7/21/2019 A2 Genetics Unit F215 Genetics
4/21
Matching airs
1# Gene A $he !osition o a gene on a chromosome#
2# Allele 9 'ach three "ases code or one amino acidand thereore the !rimar) structure#
# Genot)!e C ne orm o a gene#
;# henot)!e + $his allele is e(!ressed even i onl) one is
!resent in the genot)!e#
5# 3ocus ' $wo identical alleles make u! the genot)!e#
# +ominant ? $he 2 alleles or one gene ound on a
homologous !air o chromosomes#
@# ecessive 0 $he e(!ression o the genot)!e#
1# ?eteroB)gous 9oth alleles in the genot)!e are ull)
e(!ressed#
11# ?omoB)gous D $he genot)!e must onl) contain these
alleles i the) are to "e e(!ressed#
-
7/21/2019 A2 Genetics Unit F215 Genetics
5/21
Gregor MendelEs Monoh)"rid Crosses
MendelEs theories were diicult to acce!t ") a scientiic communit) who
knew nothing o chromosomes, genes and +/A, "ack in the latter hal o the
nineteenth centur)# $oda), however, the) can "e ull) e(!lained, i lettersare used to re!resent the alleles which code or the characteristics#
e#g# 0nvestigating $allness and dwarness in !ea !lants#
-
7/21/2019 A2 Genetics Unit F215 Genetics
6/21
$onoh#'rid crosses contin+ed alwa)s draw a genetic diagram
emem"er $wo homoB)gous !ure*"red !arents !roduce heteroB)gous F1
os!ring and mem"ers o the F1 crossed with each other !roduce anF2
generation#
1# ?untington Es chorea is a atal condition o the nervous s)stem caused ") a
dominant allele# Most suerers do not show s)m!toms until over the age o
5# A man with the disease marries and has children in his late 2s# hat is
the !ro"a"ilit) that one o his children will have inherited the condition8
2# A dog "reeder has a +almatian "itch with "lack s!ots# 9lack allele is
dominant over "rown# ?e mated the "itch with a "rown s!otted dog and
she had three "lack and one "rown s!otted !u!!ies# hat was her
genot)!e8
# An F1 generation o geraniums all had red lowers# $he F2 included somewith white lowers#
i& +raw a genetic diagram to show how this was !ossi"le#
ii& hat ratio o red: white would "e e(!ected in the F28
-
7/21/2019 A2 Genetics Unit F215 Genetics
7/21
Using genetic diagrams to solve codominance !ro"lems %!age 12
-
7/21/2019 A2 Genetics Unit F215 Genetics
8/21
2# A "udgie ancier "red homoB)gous dark "lue with homoB)gous light "lue
"irds and o"tained all mid*"lue os!ring#
?e needed more mid*"lue, so "red the F1together# '(!lain with a
genetic diagram whether he did the "est thing to !roduce ma(imum
num"ers o mid*"lue#
/ow answer the -uestions 1 and 2 on !age 12=
-
7/21/2019 A2 Genetics Unit F215 Genetics
9/21
ickle cell Anaemia codominant at the cellular level %age 12
-
7/21/2019 A2 Genetics Unit F215 Genetics
10/21
Se! 4 )ink("e
e( in mammals is inherited via a large I and a small 4 chromosome# $here is
little room on the 4 or an) genes other than that or "eing male# 4 however
is dominant to I, so onl) one 4 is needed to "e male# ?owever, linked to the I
are man) genes vital or successul lie# 0 mutations occur to an) o thesegenes then these mutations are carried through to the ne(t generation on
the I chromosome#
$he e(am!le a"ove is the inheritance o haemo!hilia, a condition that
!revents normal "lood clotting# ? is the allele or health) clotting actors,
"ut h codes or the mutation see !ower !oint and !age 12;J125 in the te(t
"ook# Answer -uestions 1, 2 and !age 125#
-
7/21/2019 A2 Genetics Unit F215 Genetics
11/21
Further Kuestions
1# '(!lain wh) a man with haemo!hilia can not !ass it on to his son#
2# $he amil) tree shows the occurrence o a genetic condition called
"rach)dact)l) %short ingers Use the tree to deduce:
a& whether the allele is dominant or recessive
"& i the condition is se( linked#
'(!lain )our answers
-
7/21/2019 A2 Genetics Unit F215 Genetics
12/21
# ne o the genes or coat colour in cats is ound on the I chromosome, "ut
not the 4# $he allele Cgives orange ur, while C9gives "lack# $he two alleles
are codominant, and when "oth are !resent the cat has !atches o orange and
"lack known as tortoiseshell#
a& '(!lain wh) male cats can not "e tortoiseshell#
"& +raw a genetic diagram to show the e(!ected genot)!es and !henot)!es o
the os!ring rom a cross "etween an orange male and a tortoiseshell emale
cat#
-
7/21/2019 A2 Genetics Unit F215 Genetics
13/21
Autosomal linkage %!age 12&
$wo genes "oth on the same chromosome tend to "e inherited together and
are thereore said to "e )inked# $he) usuall) do not show inde!endent
assortment at meta!hase 1 or 2#An e(am!le in humans is the inheritance o the gene locus or A9 "lood
grou!s and the gene locus or nail !atella s)ndrome %/& which causes short
nails and !oorl) ormed knee "ones#
$he loci are ver) close together on the chromosomes as seen in the diagram#
$he ollowing would thereore "e e(!ected to result when "lood grou! and
the s)ndrome are inherited together#
-
7/21/2019 A2 Genetics Unit F215 Genetics
14/21
hat still might rarel) ha!!en during !ro!hase 1, which ma) allow
inde!endent assortment o these alleles8
A worked e(am!le is on !age 12#
-
7/21/2019 A2 Genetics Unit F215 Genetics
15/21
Epist(sis how one gene ma) control the e(!ression o another#
age 12> ke) deinition L
+oes e!istasis reduce or increase !henot)!ic variation8
Kuite oten two or more dierent genes aect the same !henot)!e
%characteristic
?ere is an e(am!le where one gene com!lements another the) work
together#
-
7/21/2019 A2 Genetics Unit F215 Genetics
16/21
orking antagonisticall) %against one another&
$he homoB)gous !resence o a recessive allele %e!istatic allele& ma) !revent
the e(!ression o another allele at a second locus %h)!ostatic allele
/ote the e(am!le o recessive e!istasis as seen in the lower colour o
Galvia#
Another e(am!le is human e)e colour where a gene or "rown melanin !roduction is
re-uired "eore genes or how man) la)ers o melanin are to "e laid down can "e
e(!ressed#
/ow note an e(am!le o dominant e!istasis#
-
7/21/2019 A2 Genetics Unit F215 Genetics
17/21
/ote and learn the three t)!ical e!istatic ratios and answer -uestions 1 ;,
!age 12@#
/ow careull) read !age 12 a"out inheritance o com"s in domestic chickens
and coat colour in mice and then answer the -uestions 1 = %!age 1& in )our
own notes#
Finall) on this to!ic, tr) the stretch and challenge A, 9 and C -uestions#
-
7/21/2019 A2 Genetics Unit F215 Genetics
18/21
Contin+o+s (nd Discontin+o+s &(ri(tion %!age 1
-
7/21/2019 A2 Genetics Unit F215 Genetics
19/21
Genot#pe (nd En:ironment contri'+te to the Phenot#pe
/ow answer -uestion
1 on !age 1=
-
7/21/2019 A2 Genetics Unit F215 Genetics
20/21
Can )ou think o an) o"vious e(am!les and are the) discontinuous or
continuous e(am!les8 Give detail#
Man) o the traits re-uired in agriculture are !ol)genic so the stud) o this
t)!e o genetics is ver) useul or !lant and arm animal "reeders#
ee !ower !oint e(am!les and answer -uestions 1 !age 1=#
-
7/21/2019 A2 Genetics Unit F215 Genetics
21/21
top related