To answer this question, you must have first completed Activity 2.1 Down's syndrome, in Topic 4, Section 2.2.2. In this activity, you were required to download the document named 'Birth Summary Tables from 1938 to XXXX' (this will be the most recent year available before module start) located in the Resources area of the module website.

Once you had opened the file and located Table 2 'Live births by age of mother' you were asked to do the following:

Live births by

Source: Office for National Statistics

Year	Age of mother at birth (years)
All ages1	Under 20	20 to 24	25 to 29	30 to 34	35 to 39	40 and over
2020	613,936	15,940	79,626	164,765	205,675	118,426	29,412
2019	640,370	17,720	86,756	173,944	209,905	122,409	29,618
2018	657,076	18,976	91,095	180,858	212,707	124,567	28,865
2017	679,106	20,358	97,506	190,028	216,787	125,114	29,313
2016	696,271	22,465	102,607	196,132	220,129	125,205	29,733
2015	697,852	23,948	108,111	198,183	217,755	120,614	29,241
2014	695,233	25,977	112,615	196,818	215,642	115,171	29,010
2013	698,512	29,136	119,719	196,693	212,306	111,500	29,158
2012	729,674	33,815	132,456	202,370	216,242	114,797	29,994
2011	723,913	36,435	134,946	200,587	207,151	115,444	29,350
2010	723,165	40,591	137,312	199,233	202,457	115,841	27,731
2009	706,248	43,243	136,012	194,129	191,600	114,288	26,976
2008	708,711	44,691	135,971	192,960	192,450	116,220	26,419
2007	690,013	44,805	130,784	182,570	191,124	115,380	25,350
2006	669,601	45,509	127,828	172,642	189,407	110,509	23,706
2005	645,835	44,830	122,145	164,348	188,153	104,113	22,246
2004	639,721	45,094	121,072	159,984	190,550	102,228	20,793
2003	621,469	44,236	116,622	156,931	187,214	97,386	19,080
2002	596,122	43,467	110,959	153,379	180,532	90,449	17,336
2001	594,634	44,189	108,844	159,926	178,920	86,495	16,260
2000	604,441	45,846	107,741	170,701	180,113	84,974	15,066
1999	621,872	48,375	110,722	181,931	185,311	81,281	14,252
1998	635,901	48,285	113,537	193,144	188,499	78,881	13,555
1997	643,095	46,372	118,589	202,792	187,528	74,900	12,914
1996	649,485	44,667	125,732	211,103	186,377	69,503	12,103
1995	648,138	41,938	130,744	217,418	181,202	65,517	11,319
1994	664,726	42,026	140,240	229,102	179,568	63,061	10,729
1993	673,467	45,121	151,975	235,961	171,061	58,824	10,525
1992	689,656	47,861	163,311	244,798	166,839	56,650	10,197
1991	699,217	52,396	173,356	248,727	161,259	53,644	9,835
1990	706,140	55,541	180,136	252,577	156,264	51,905	9,717
1989	687,725	55,543	185,239	242,822	145,320	49,465	9,336
1988	693,577	58,741	193,726	243,460	140,974	47,649	9,027
1987	681,511	57,545	193,232	238,929	136,558	46,604	8,643
1986	661,018	57,406	192,064	229,035	129,487	45,465	7,561
1985	656,417	56,929	193,958	227,486	126,185	44,393	7,466
1984	636,818	54,508	191,455	218,031	122,774	42,921	7,129
1983	629,134	54,059	191,852	214,078	120,996	41,277	6,872
1982	625,931	55,435	192,322	211,905	120,758	38,992	6,519
19813	634,492	56,570	194,500	215,760	126,590	34,210	6,860
1980	656,234	60,754	201,541	223,438	129,908	33,893	6,700
1979	638,028	59,143	193,209	222,102	125,664	31,394	6,516
1978	596,418	55,984	182,580	210,598	113,077	27,937	6,242
1977	569,259	54,477	174,544	207,916	100,807	25,527	5,988
1976	584,270	57,943	182,210	220,712	90,791	26,117	6,497
1975	603,445	63,507	190,198	225,990	88,379	28,147	7,224
1974	639,885	68,724	208,084	235,593	89,132	30,308	8,044
1973	675,953	73,270	223,675	243,753	91,800	34,178	9,277
1972	725,440	79,087	249,109	247,676	98,739	39,821	11,008
1971	783,155	82,641	285,703	247,239	109,616	45,224	12,732
1970	784,486	80,975	289,209	238,228	114,086	48,323	13,665
1969	797,538	81,659	289,012	238,381	120,395	52,843	15,248
1968	819,272	82,075	295,946	240,807	125,316	58,083	17,045
1967	832,164	84,542	291,656	243,802	130,279	63,085	18,800
1966	849,823	86,746	285,808	253,743	136,406	67,036	20,084
1965	862,725	81,611	278,874	263,395	144,638	72,022	22,185
1964	875,972	76,734	276,103	270,700	153,513	75,371	23,551
1963	854,055	71,640	267,559	263,241	153,696	74,401	23,518
1962	838,736	67,334	260,882	256,386	153,985	76,219	23,930
1961	811,281	59,786	249,829	248,540	152,286	77,516	23,324
1960	785,005	51,645	240,128	242,939	150,663	77,603	22,027
1959	748,501	46,067	229,064	233,579	143,475	77,261	19,055
1958	740,715	43,831	221,938	234,046	144,266	76,916	19,718
1957	723,381	41,228	211,654	230,565	143,736	75,147	21,051
1956	700,335	37,938	203,893	222,720	142,976	70,998	21,810
1955	667,811	32,947	192,555	212,187	141,542	66,410	22,170
1954	673,651	31,709	193,627	211,567	149,162	64,334	23,252
1953	684,372	30,417	194,765	216,697	150,639	68,468	23,386
1952	673,735	29,148	189,342	214,402	144,569	72,422	23,852
1951	677,529	29,111	187,514	219,064	140,231	77,167	24,442
1950	697,097	30,847	190,644	228,968	137,581	83,040	26,017
1949	730,518	31,850	200,945	245,253	137,128	87,631	27,711
1948	775,306	30,454	210,120	249,889	156,083	97,434	31,326
1947	881,026	27,747	227,598	281,454	195,181	114,350	34,696
1946	820,719	24,816	195,225	248,121	202,752	116,021	33,784
1945	679,937	25,437	174,869	182,212	163,501	101,089	32,829
1944	751,478	24,725	193,473	201,886	187,041	110,475	33,878
1943	684,334	24,262	176,262	195,762	163,937	93,421	30,690
1942	651,503	24,031	165,269	200,524	149,874	83,240	28,565
1941	579,091	24,499	147,563	180,475	127,268	73,028	26,258
1940	590,120	26,270	142,100	191,027	133,335	72,375	25,013
1939	614,479	28,788	139,504	199,877	143,510	77,179	25,621
19384	621,204	25,410	146,675	199,931	145,353	77,276	26,559

• i.Find the number of live births in 1940 for women in the maternal age ranges: under 20, 25 to 29 and 35 to 39. Repeat this for the most recently presented year, then for the year of your birth, and two other years in different decades - In total, you should have collected data for five different years.
• ii. You were then required to plot a computer-generated x-y scatter graph showing the number of live births for the selected age ranges and birth years in chronological order (an example of how your graph might look is provided within the activity).

Answering this question

You will be awarded up to 13 marks for Question 1 as follows:

• a.Plot your dataset in the form of a line graph using a computer programme to generate the x-y scatter graph. Your graph should have a title, a legend and each axis labelled appropriately. You should also present your dataset in the form of a table.
• b.Using the information presented in your graph and table, answer the following questions:
  • i.What trend is seen over time in the number of births to women in the different age categories?
  • ii. Based on the information presented in Topic 4, what is your prediction for the incidence of Down's syndrome? Briefly, explain your reasoning.
  • 2.2.1 Down's syndrome

TOPIC 4

Down's syndrome (DS) (Figure2.4) is named after the British physician John Down, who first described the condition. It is one of the most common genetic disorders and occurs in 1 out of every 600-700births. The characteristics of DS vary between individuals but typically include problems with the cardiovascular, musculoskeletal and digestive systems, as well as metabolic disorders, abnormal immune function and endocrine disruption (Mazurek and Wyca, 2015).

In addition, almost all DS individuals have some form of intellectual disability and problems with memory and perception.

Related to this, most adults with DS will developdementia, a set of symptoms that include memory loss and difficulties with reasoning and problem-solving. Many of these symptoms overlap with the dementia that is observed inAlzheimer's disease (AD). You may already be familiar with AD, as it is the most common cause of dementia in people over the age of 65. In most cases, the cause of AD is idiopathic and relates to both genetic and environmental factors. However, a small subset of people will develop early-onset AD before 65 years of age due to mutations in the gene encoding theamyloid precursor protein (APP)or a related protein presenilin.

2.2.2Genetics of Down's syndrome

Why do people with DS develop AD-like dementia? The answer lies on chromosome21. Individuals with DS inherit three copies of chromosome21 (trisomy21) (Figure2.5).

Figure2.5Karyotype of trisomy 21.

Long description

How many copies of each chromosome are usually found in a human cell?

1

2

3

4

Answer

There are usually two copies of each chromosome in a human cell. One chromosome is inherited from the mother and one from the father.

Does the karyotype in Figure2.5 come from a male or female? (See Topic1Human variation and diversity.)

MaleCorrect. The karyotype shows the presence of an X and a Ychromosome; therefore the individual is a male.

Female

Although it is not known why trisomy occurs, it is thought to relate to the process of meiosis during the maturation of oocytes (eggs) over a woman's lifetime. You will learn more about the reproductive system if you choose to study Topic10Reproduction, but for now all you need to know is that older women are at higher risk of having a baby with DS than young women.

The gene that codes for APP is located on chromosome21. Therefore, people with DS make higher amounts of APP than usual. The process by which APP is cut into smaller pieces to generate theamyloid-(A)protein is detailed in Video2.6.

Video player: Video2.6 (slidecast)

Video2.6 (slidecast)Processing of the amyloid precursor protein (APP) to generate amyloid-.

As levels of A build up in the brain, they cause synaptic dysfunction that impairs neuronal communication. Eventually this impairment causes the neurons to die. For reasons that are not fully understood, neurons in the hippocampus and frontal cortex are particularly vulnerable to death.

What aspects of brain function would you predict to be affected by neuronal loss in the hippocampus and frontal cortex? (Refer to Section1.2.1.)

Hide answer

Loss of neurons in the hippocampus would lead to memory problems, particularly the ability to form new long-term memories. Damage to the frontal cortex would affect aspects of personality, reasoning and other higher cognitive functions, as well as some aspects of vision and hearing.

Because people with DS make more APP from birth, they generate more -amyloid over their lifetime and develop neuronal death at an earlier age. Therefore, the brain of a 40-year-old with DS will look similar to that of a 70-year-old with AD (Figure2.6).

Figure2.6Coronal section of brain from a healthy person (a) and someone with AD (b).

Long description

Look at the two brain sections in Figure2.6. What differences do you see between them?

Reveal answer

Activity 2.1Down's syndrome

Timing:Allow about 3 hours

This activity will form part of your submission for TMA02.

In this activity, you will estimate the future incidence of Down's syndrome based on the birth rates for women in England and Wales.

Incidenceis a medical term that refers to the number ofnewcases diagnosed in a population over a given time period. This is different from the termprevalence, which is a measurement of thetotalnumber of cases in the population at a given time.

Here's my table:

Number of live births for women in the maternal age ranges

Year	Under 20	25 to 29	35 to 39
1940	26,270	191,027	72,375
1970	80,975	238,228	48,323
1980	60,754	223,438	33,893
1990	55,541	252,577	51,905
2020	15,940	164,765	118,426

References

Chen, J. W., Gombart, Z. J., Rogers, S., Gardiner, S. K., Cecil, S. and Bullock, R. M. (2011) 'Pupillary reactivity as an early indicator of increased intracranial pressure: The introduction of the neurological pupil index',Surgical Neurology International, vol. 2, p. 82 [Online]. Available at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3130361/ (Accessed 6 September 2017).

Cooke Bailey, J. N., Hoffman, J. D., Sardell, R. J., Scott, W. K., Pericak-Vance, M. A. and Haines, J. L. (2016) 'The application of genetic risk scores in age-related macular degeneration: A review',Journal of Clinical Medicine, vol.5, no.3, p.31 [Online]. Available at http://www.mdpi.com/2077-0383/5/3/31 (Accessed 6 September 2017).

Davies, M. (2003) 'The role of GABA_Areceptors in mediating the effects of alcohol in the central nervous system',Journal of Psychiatry and Neuroscience, vol.28, no.4, pp.263-74.

Drayna, D. (2005) 'Human taste genetics',Annual Review of Genomics and Human Genetics, vol.6, pp.217-35 [Online]. Available at http://www.annualreviews.org/doi/abs/10.1146/annurev.genom.6.080604.162340 (Accessed 6 September 2017).

Mazurek, D. and Wyka, J. (2015) 'Down syndrome - genetic and nutritional aspects of accompanying disorders',Roczniki Panstwowego Zakladu Higieny, vol.66, no.3, pp.189-94.

Schepers, R. J. and Ringkamp, M. (2010) 'Thermoreceptors and thermosensitive afferents',Neuroscience and Biobehavioral Reviews, vol.34, no.2, pp.177-84 [Online]. Available at https://www.ncbi.nlm.nih.gov/pubmed/19822171 (Accessed 6 September 2017).

Spence, C. (2015) 'Just how much of what we taste derives from the sense of smell?',Flavour, vol. 4, no. 30 [Online]. Available at https://flavourjournal.biomedcentral.com/articles/10.1186/s13411-015-0040-2 (Accessed 6 September 2017).

Williams, W. C. (1923) 'XXII',Spring and All, Paris, Contact Publishing Co.

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